Method of Producing Anode or Cathode Participates for Alkali Metal Batteries

ABSTRACT

Provided is method of producing anode or cathode particulates for an alkali metal battery. The method comprises: (a) preparing a slurry containing particles of an anode or cathode active material, an electron-conducting material, and an electrolyte containing a lithium salt or sodium salt and an optional polymer dissolved in a liquid solvent; and (b) conducting a particulate-forming means to convert the slurry into multiple anode or cathode particulates, wherein an anode or a cathode particulate is composed of (i) particles of the active material, (ii) the electron-conducting material, and (iii) an electrolyte, wherein the electron-conducting material forms a 3D network of electron-conducting pathways and the electrolyte forms a 3D network of lithium ion- or sodium ion-conducting channels and wherein the anode particulate or cathode particulate has a dimension from 10 nm to 100 μm and an electrical conductivity from about 10 −6  S/cm to about 300 S/cm.

FIELD OF THE INVENTION

The present invention relates to the field of alkali batteries (e.g.lithium or sodium batteries), including primary (non-rechargeable) andsecondary (rechargeable) alkali metal batteries and alkali ion batterieshaving a new structure and geometry that deliver both high energydensities and high power densities.

BACKGROUND OF THE INVENTION

Historically, today's most favorite rechargeable energy storagedevices—lithium-ion batteries—actually evolved from rechargeable“lithium metal batteries” using lithium (Li) metal or Li alloy as theanode and a Li intercalation compound as the cathode. Li metal is anideal anode material due to its light weight (the lightest metal), highelectronegativity (−3.04 V vs. the standard hydrogen electrode), andhigh theoretical capacity (3,860 mAh/g). However, there are safetyproblems caused by sharply uneven Li growth (formation of Li dendrites)as the metal is re-plated during each subsequent recharge cycle. As thenumber of cycles increases, these dendritic or tree-like Li structurescould eventually traverse the separator to reach the cathode, causinginternal short-circuiting.

To overcome these safety issues, several alternative approaches wereproposed in which either the electrolyte or the anode was modified. Oneapproach involved replacing Li metal by graphite (another Li insertionmaterial) as the anode. The operation of such a battery involvesshuttling Li ions between two Li insertion compounds, hence the name“Li-ion battery.” Presumably because of the presence of Li in its ionicrather than metallic state, Li-ion batteries are inherently safer thanLi-metal batteries. Lithium ion battery is a prime candidate energystorage device for electric vehicle (EV), renewable energy storage, andsmart grid applications.

As a totally distinct class of energy storage device, sodium batterieshave been considered an attractive alternative to lithium batteriessince sodium is abundant and the production of sodium is significantlymore environmentally benign compared to the production of lithium. Inaddition, the high cost of lithium is a major issue and Na batteriespotentially can be of significantly lower cost.

There are at least two types of batteries that operate on bouncingsodium ions (Na⁺) back and forth between an anode and a cathode: thesodium metal battery having Na metal or alloy as the anode activematerial and the sodium-ion battery having a Na intercalation compoundas the anode active material. Sodium ion batteries using a hardcarbon-based anode active material (a Na intercalation compound) and asodium transition metal phosphate as a cathode have been described byseveral research groups; e.g. J. Barker, et al. “Sodium Ion Batteries,”U.S. Pat. No. 7,759,008 (Jul. 20, 2010).

However, these sodium ion-based devices exhibit even lower specificenergies and rate capabilities than Li-ion batteries. The anode activematerials for Na intercalation and the cathode active materials for Naintercalation have lower Na storage capacities as compared with their Listorage capacities. For instance, hard carbon particles are capable ofstoring Li ions up to 300-360 mAh/g, but the same materials can store Naions up to 150-250 mAh/g and less than 100 mAh/g for K ion storage.

Instead of hard carbon or other carbonaceous intercalation compound,sodium metal may be used as the anode active material in a sodium metalcell. However, the use of metallic sodium as the anode active materialis normally considered undesirable and dangerous due to the dendriteformation, interface aging, and electrolyte incompatibility problems.

Low-capacity anode or cathode active materials are not the only problemthat the alkali metal-ion battery industry faces. There are seriousdesign and manufacturing issues that the lithium-ion battery industrydoes not seem to be aware of, or has largely ignored. For instance,despite the high gravimetric capacities at the electrode level (based onthe anode or cathode active material weight alone) as frequently claimedin open literature and patent documents, these electrodes unfortunatelyfail to provide batteries with high capacities at the battery cell orpack level (based on the total battery cell weight or pack weight). Thisis due to the notion that, in these reports, the actual active materialmass loadings of the electrodes are too low. In most cases, the activematerial mass loadings of the anode (areal density) is significantlylower than 15 mg/cm² and mostly <8 mg/cm² (areal density=the amount ofactive materials per electrode cross-sectional area along the electrodethickness direction). The cathode active material amount is typically1.5-2.5 times higher than the anode active material. As a result, theweight proportion of the anode active material (e.g. graphite or carbon)in a lithium-ion battery is typically from 12% to 17%, and that of thecathode active material (e.g. LiMn₂O₄) from 17% to 35% (mostly <30%).The weight fraction of the cathode and anode active materials combinedis typically from 30% to 45% of the cell weight

The low active material mass loading is primarily due to the inabilityto obtain thicker electrodes (thicker than 100-200 μm) using theconventional slurry coating procedure. This is not a trivial task as onemight think and, in reality, the electrode thickness is not a designparameter that can be arbitrarily and freely varied for the purpose ofoptimizing the cell performance. Contrarily, thicker electrodes wouldrequire excessively long oven-drying zones that could run over 100meters for an electrode thickness of 100 μm. Furthermore, thickersamples tend to become extremely brittle or of poor structural integrityand would also require the use of large amounts of binder resin. The lowareal densities and low volume densities (related to thin electrodes andpoor packing density) result in a relatively low volumetric capacity andlow volumetric energy density of the battery cells. Sodium-ion batteriesand potassium-ion batteries have similar problems.

With the growing demand for lighter weight, more compact and portableenergy storage systems, there is keen interest to increase theutilization of the volume of the batteries. Novel electrode materialsand designs that enable high volumetric capacities and high massloadings are essential to achieving improved cell volumetric capacitiesand energy densities for alkali metal batteries.

Therefore, there is clear and urgent need for alkali metal batteriesthat have high active material mass loading (high areal density), highelectrode volume without significantly decreasing the electron and iontransport rates (e.g. without a high electron transport resistance orlong lithium or sodium ion diffusion path), high volumetric capacity,high energy density, and high power density.

SUMMARY OF THE INVENTION

The present invention provides a method of producing anode particulatesor cathode particulates for use in an alkali metal battery. The methodcomprises:

-   -   (a) preparing a slurry containing particles of an anode or        cathode active material capable of reversibly absorbing and        desorbing lithium ions or sodium ions, an electron-conducting        material, and an electrolyte containing a lithium salt or sodium        salt and an optional polymer dissolved in a liquid solvent; and    -   (b) conducting a particulate-forming means to convert the slurry        into multiple anode particulates or cathode particulates,        wherein an anode particulate or a cathode particulate is        composed of (i) particles of the anode or cathode active        material, (ii) the electron-conducting material, and (iii) an        electrolyte, wherein the electron-conducting material forms a 3D        network of electron-conducting pathways in electronic contact        with the anode or cathode active material and the electrolyte        forms a 3D network of lithium ion- or sodium ion-conducting        channels in ionic contact with the anode or cathode active        material and wherein the anode particulate or cathode        particulate has a dimension from 10 nm to 100 μm and an        electrical conductivity from about 10⁻⁶ S/cm to about 300 S/cm.

Preferably, the particulate-forming means is selected from pan-coatingmethod, air-suspension coating method, centrifugal extrusion, vibrationnozzle method, spray-drying, Interfacial polycondensation or interfacialcross-linking, in situ polymerization, matrix polymerization, or acombination thereof.

In some embodiments, the present invention provides a unique anodematerial composition for an alkali metal battery (e.g. lithium batteryor sodium battery). The anode composition is in a form of particulates,wherein a particulate preferably has a dimension (e.g. diameter,thickness, etc.) from 10 nm to 300 μm and, more preferably, from 100 nmto 100 μm and further preferably from 1 to 20 μm.

In certain embodiments, the particulate comprises: (i) an anode activematerial capable of reversibly absorbing and desorbing lithium ions orsodium ions, (ii) an electron-conducting material (e.g. a conductivepolymer, carbon nanotubes, carbon nanofibers, graphene sheets, etc.),and (iii) a lithium ion-conducting or sodium ion-conducting electrolyte,wherein the electron-conducting material forms a 3D network ofelectron-conducting pathways in electronic contact with the anode activematerial and the electrolyte forms a 3D network of lithium ion- orsodium ion-conducting channels in ionic contact with the anode activematerial and wherein said anode particulate has an electricalconductivity from about 10⁻⁷ S/cm to about 300 S/cm (preferably >10⁻⁵S/cm). The anode particulate may further comprise a resin binder ormatrix, which is not required or desired.

In certain embodiments, the alkali metal battery is a lithium-ionbattery and the anode active material is selected from the groupconsisting of: (a) particles of natural graphite, artificial graphite,mesocarbon microbeads (MCMB), needle coke, carbon particles, carbonfibers, carbon nanotubes, and carbon nanofibers; (b) silicon (Si),germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc(Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium(Ti), iron (Fe), and cadmium (Cd); (c) alloys or intermetallic compoundsof Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, or Cd with other elements, whereinsaid alloys or compounds are stoichiometric or non-stoichiometric; (d)oxides, carbides, nitrides, sulfides, phosphides, selenides, andtellurides of Si, Ge, Sn, Nb, Mo, Pb, Sb, Bi, Zn, Al, Fe, Ni, Co, Ti,Mn, or Cd, and their mixtures or composites; (e) prelithiated versionsthereof; (f) prelithiated graphene sheets; and (g) combinations thereof.

In certain preferred embodiments, the anode active material contains aprelithiated Si, prelithiated Ge, prelithiated Sn, prelithiated SnO_(x),prelithiated SiO_(x), prelithiated iron oxide, prelithiated VO₂,prelithiated Co₃O₄, prelithiated Ni₃O₄, prelithiated Mn₃O₄, prelithiatedTiNb₂O₇, Li₄Ti₅O₁₂, or a combination thereof, wherein x=1 to 2.

The prelithiated graphene sheets are selected from prelithiated versionsof pristine graphene, graphene oxide, reduced graphene oxide, graphenefluoride, graphene chloride, graphene bromide, graphene iodide,hydrogenated graphene, nitrogenated graphene, boron-doped graphene,nitrogen-doped graphene, chemically functionalized graphene, aphysically or chemically activated or etched version thereof, or acombination thereof.

In certain other embodiments, the alkali metal battery is a sodium-ionbattery and the anode active material contains an alkali intercalationcompound selected from the following groups of materials: (a) sodium- orpotassium-doped silicon (Si), germanium (Ge), tin (Sn), lead (Pb),antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), titanium (Ti),cobalt (Co), nickel (Ni), manganese (Mn), cadmium (Cd), and mixturesthereof; (b) Sodium- or potassium-containing alloys or intermetalliccompounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Co, Ni, Mn, Cd, andtheir mixtures; (c) sodium- or potassium-containing oxides, carbides,nitrides, sulfides, phosphides, selenides, tellurides, or antimonides ofSi, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ti, Co, Ni, Mn, Cd, and mixtures orcomposites thereof; (d) sodium or potassium salts; and (e) graphenesheets pre-loaded with sodium or potassium.

In some preferred embodiments, the alkali metal battery is a sodium-ionbattery and the anode active material contains an alkali intercalationcompound selected from petroleum coke, carbon black, amorphous carbon,activated carbon, hard carbon, soft carbon, templated carbon, hollowcarbon nanowires, hollow carbon sphere, titanates, NaTi₂(PO₄)₃,Na₂Ti₃O₇, Na₂C₈H₄O₄, Na₂TP, Na_(x)TiO₂ (x=0.2 to 1.0), Na₂C₈H₄O₄,carboxylate based materials, C₈H₄Na₂O₄, C₈H₆O₄, C₈H₅NaO₄, C₈Na₂F₄O₄,C₁₀H₂Na₄O₈, C₁₄H₄O₆, C₁₄H₄Na₄O₈, or a combination thereof.

Preferably, the anode active material is in a form of nanoparticle,nanowire, nanofiber, nanotube, nanosheet, nanobelt, nanoribbon,nanodisc, nanoplatelet, or nanohorn having a thickness or diameter from0.5 nm to 100 nm (preferably no greater than 20 nm). The anode activematerial may be coated with a layer of carbon, a conducting polymer, ora graphene sheet.

In the anode particulate, the electron-conducting polymer may beselected from polyaniline, polypyrrole, polythiophene, polyfuran, abi-cyclic polymer, a sulfonated derivative thereof, or a combinationthereof.

There is no restriction on the type of electrolyte that can be used.However, preferably, the electrolyte has a lithium ion conductivity orsodium ion conductivity no less than 10⁻⁷ S/cm at room temperature andmore preferably from 10⁻⁵ S/cm to 5×10⁻² S/cm. The electrolyte may beselected from an aqueous electrolyte, an organic liquid electrolyte, anionic liquid electrolyte, a polymer gel electrolyte, a polymerelectrolyte, an inorganic solid-state electrolyte, a quasi-solidelectrolyte, or a combination thereof.

In the anode particulate, the electron-conducting material may beselected from a conducting polymer, a carbon fiber or graphite fiber, acarbon nanotube, a carbon nanofiber, a graphitic nanofiber, a conductivepolymer fiber, a metal nanowire, a metal-coated fiber, a graphene sheet,an expanded graphite platelet, carbon black, acetylene black, needlecoke, or a combination thereof.

The present invention also provides a powder mass containing a pluralityof the anode particulates as defined the foregoing paragraphs. Theinvention also provides an anode containing multiple anode particulatesof the present invention, each composed of (i) an anode active materialcapable of reversibly absorbing and desorbing lithium ions or sodiumions, (ii) an electron-conducting material (e.g. a conductive polymer,carbon nanotubes, carbon nanofibers, graphene sheets, etc.), and (iii) alithium ion-conducting or sodium ion-conducting electrolyte, wherein theelectron-conducting material forms a three dimensional (3D) network ofelectron-conducting pathways in electronic contact with the anode activematerial and the electrolyte forms a 3D network of lithium ion- orsodium ion-conducting channels in ionic contact with the anode activematerial.

When these multiple particulates are packed together to form an anodeelectrode, the 3D network of electron-conducting pathways in individualparticulates are merged into an extensive or large 3D network ofelectron-conducting pathways that can cover the entire anode electrode.Further, when these multiple particulates are packed together to form ananode electrode, the 3D network of ion-conducting channels in individualparticulates are merged into an extensive or large 3D network of lithiumion- or sodium ion-conducting channels that can cover the entire anodeelectrode.

The invention also provides a lithium battery or sodium battery, whichcontains an optional anode current collector, the anode as definedabove, a cathode containing a cathode active material, an optionalcathode current collector, an electrolyte in ionic contact with theanode and the cathode, and an optional porous separator. Thiselectrolyte can be the same as or different than the electrolytedisposed in the individual anode particulates.

Preferably, the cathode also contains multiple cathode particulates,wherein a cathode particulate is composed of (i) a cathode activematerial capable of reversibly absorbing and desorbing lithium ions orsodium ions, (ii) an electron-conducting material (e.g. a conductivepolymer, carbon nanotubes, carbon nanofibers, graphene sheets, etc.),and (iii) a lithium ion-conducting or sodium ion-conducting electrolyte,wherein the electron-conducting material forms a 3D network ofelectron-conducting pathways in electronic contact with the cathodeactive material and the electrolyte forms a 3D network of lithium ion-or sodium ion-conducting channels in ionic contact with the cathodeactive material, and wherein said anode particulate has an electricalconductivity from about 10⁻⁷ S/cm to about 300 S/cm. The cathodeparticulate preferably has a dimension from 10 nm to 300 μm and anelectrical conductivity from about 10⁻⁷ S/cm to about 300 S/cm. Theelectrolyte in the cathode particulates can be different than or thesame as the electrolyte in the anode particulates.

The invention also provides a powder mass containing multiple cathodeparticulates as defined above. Also provided is a cathode electrodecontaining multiple cathode particulates of this nature.

The invented lithium battery or sodium battery may be a lithium-ionbattery, sodium-ion battery, lithium metal battery, sodium metalbattery, lithium-sulfur battery, room temperature sodium-sulfur battery,lithium-selenium battery, sodium-air battery, or lithium-air battery.

In certain embodiments, the invented battery is a sodium battery,wherein the anode contains the presently invented anode particulates andthe cathode contains a cathode active material (preferably also in thepresently invented cathode particulate form) containing a sodiumintercalation compound or a potassium intercalation compound selectedfrom NaFePO₄, Na_((1-x))K_(x)PO₄, KFePO₄, Na_(0.7)FePO₄,Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃, Na₃V₂(PO₄)₂F₃, Na₂FePO₄F, NaFeF₃,NaVPO₄F, KVPO₄F, Na₃V₂(PO₄)₂F₃, Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃,NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅, Na_(x)CoO₂,Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂, Na_(x)(Fe_(1/2)Mn_(1/2))O₂, Na_(x)MnO₂,λ-MnO₂, Na_(x)K_((1-x))MnO₂, Na_(0.44)MnO₂, Na_(0.44)MnO₂/C, Na₄Mn₉O₁₈,NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇, Ni_(1/3)Mn_(1/3)Co_(1/3)O₂,Cu_(0.56)Ni_(0.44)HCF, NiHCF, Na_(x)MnO₂, NaCrO₂, KCrO₂, Na₃Ti₂(PO₄)₃,NiCo₂O₄, Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C, NaV_(1-x)Cr_(x)PO₄F,Se_(z)S_(y), y/z=0.01 to 100, Se, sodium polysulfide, sulfur,Alluaudites, or a combination thereof, wherein x is from 0.1 to 1.0.

In the presently invented lithium battery or sodium battery, the cathodeactive material may comprise an alkali metal intercalation compound oralkali metal-absorbing compound selected from an inorganic material, anorganic or polymeric material, a metal oxide/phosphate/sulfide, or acombination thereof. Preferably, the cathode active material is also inthe presently invented particulate form.

In certain preferred embodiments, the metal oxide/phosphate/sulfide isselected from a lithium cobalt oxide, lithium nickel oxide, lithiummanganese oxide, lithium vanadium oxide, lithium-mixed metal oxide,lithium iron phosphate, lithium manganese phosphate, lithium vanadiumphosphate, lithium mixed metal phosphate, transition metal sulfide,transition metal fluoride, transition metal chloride, or a combinationthereof.

The inorganic material is selected from sulfur, sulfur compound, lithiumpolysulfide, transition metal dichalcogenide, a transition metaltrichalcogenide, or a combination thereof. The inorganic material isselected from: (a) bismuth selenide or bismuth telluride, (b) transitionmetal dichalcogenide or trichalcogenide, (c) sulfide, selenide, ortelluride of niobium, zirconium, molybdenum, hafnium, tantalum,tungsten, titanium, cobalt, manganese, iron, nickel, or a transitionmetal; (d) boron nitride, or (e) a combination thereof. Preferably, theinorganic material is selected from TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, CoO₂,an iron oxide, a vanadium oxide, or a combination thereof.

In certain embodiments, the metal oxide/phosphate/sulfide contains avanadium oxide selected from the group consisting of VO₂, Li_(x)VO₂,V₂O₅, Li_(x)V₂O₅, V₃O₈, Li_(x)V₃O₈, Li_(x)V₃O₇, V₄O₉, Li_(x)V₄O₉, V₆O₁₃,Li_(x)V₆O₁₃, their doped versions, their derivatives, and combinationsthereof, wherein 0.1<x<5.

In certain embodiments, in the invented lithium battery or sodiumbattery, the metal oxide/phosphate/sulfide is selected from a layeredcompound LiMO₂, spinel compound LiM₂O₄, olivine compound LiMPO₄,silicate compound Li₂MSiO₄, Tavorite compound LiMPO₄F, borate compoundLiMBO₃, or a combination thereof, wherein M is a transition metal or amixture of multiple transition metals.

In the lithium battery or sodium battery, the organic material orpolymeric material may be selected from Poly(anthraquinonyl sulfide)(PAQS), a lithium oxocarbon, 3,4,9,10-perylenetetracarboxylicdianhydride (PTCDA), poly(anthraquinonyl sulfide),pyrene-4,5,9,10-tetraone (PYT), polymer-bound PYT, Quino(triazene),redox-active organic material, Tetracyanoquino-dimethane (TCNQ),tetracyanoethylene (TCNE), 2,3,6,7,10,11-hexamethoxytriphenylene (HMTP),poly(5-amino-1,4-dyhydroxy anthraquinone) (PADAQ), phosphazene disulfidepolymer ([(NPS₂)₃]n), lithiated 1,4,5,8-naphthalenetetraol formaldehydepolymer, Hexaazatrinaphtylene (HATN), Hexaazatriphenylenehexacarbonitrile (HAT(CN)₆), 5-Benzylidene hydantoin, Isatine lithiumsalt, Pyromellitic diimide lithium salt, tetrahydroxy-p-benzoquinonederivatives (THQLi₄), N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.

The thioether polymer is selected fromPoly[methanetetryl-tetra(thiomethylene)] (PMTTM),Poly(2,4-dithiopentanylene) (PDTP), a polymer containingPoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, Poly(2-phenyl-1,3-dithiolane) (PPDT),Poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT),poly[1,2,4,5-tetrakis(propylthio)benzene] (PTKPTB, orpoly[3,4(ethylenedithio)thiophene] (PEDTT).

In certain embodiments, the organic material contains a phthalocyaninecompound selected from copper phthalocyanine, zinc phthalocyanine, tinphthalocyanine, iron phthalocyanine, lead phthalocyanine, nickelphthalocyanine, vanadyl phthalocyanine, fluorochromium phthalocyanine,magnesium phthalocyanine, manganous phthalocyanine, dilithiumphthalocyanine, aluminum phthalocyanine chloride, cadmiumphthalocyanine, chlorogallium phthalocyanine, cobalt phthalocyanine,silver phthalocyanine, a metal-free phthalocyanine, a chemicalderivative thereof, or a combination thereof.

Preferably, the cathode active material contains an alkali metalintercalation compound or alkali metal-absorbing compound selected froman oxide, dichalcogenide, trichalcogenide, sulfide, selenide, ortelluride of niobium, zirconium, molybdenum, hafnium, tantalum,tungsten, titanium, vanadium, chromium, cobalt, manganese, iron, ornickel which are in a nanowire, nanodisc, nanoribbon, or nanoplateletform having a thickness or diameter less than 100 nm, preferably <50 nm,and most preferably <20 nm.

In certain embodiments, the method further comprises a step ofcompacting or merging a plurality of the anode particulates to form ananode electrode wherein, prior to the anode electrode formation, eachanode particulate has an electron-conducting material forming a 3Dnetwork of electron-conducting pathways in electronic contact with theanode active material and the electrolyte in each particulate forms a 3Dnetwork of lithium ion- or sodium ion-conducting channels in ioniccontact with the anode active material and wherein, after the anodeelectrode formation, a plurality of 3D networks of electron-conductingpathways in the plurality of anode particulates are merged into onelarge 3D network of electron-conducting pathways substantially extendedthroughout the entire anode electrode and wherein a plurality of 3Dnetworks of lithium ion- or sodium ion-conducting channels in theplurality of anode particulates are merged into one giant 3D network oflithium ion- or sodium ion-conducting channels substantially extendedthroughout the entire anode electrode. A binder resin may be used tobond these anode particulates together.

The method may further comprise combining an optional anode currentcollector, the aforementioned anode electrode, a porous separator orsolid-state electrolyte, a cathode electrode, and an optional cathodecurrent collector to form an alkali metal battery. Optionally, a liquidelectrolyte may be introduced into the battery cell.

In certain embodiments, the method further comprises a step ofcompacting, merging, or bonding a plurality of the cathode particulatesto form a cathode electrode wherein, prior to the cathode electrodeformation, each particulate has an electron-conducting material forminga 3D network of electron-conducting pathways in electronic contact withthe cathode active material and the electrolyte in each particulateforms a 3D network of lithium ion- or sodium ion-conducting channels inionic contact with the cathode active material and wherein, after thecathode electrode formation, a plurality of 3D networks ofelectron-conducting pathways in the plurality of cathode particulatesare merged into one giant 3D network of electron-conducting pathwayssubstantially extended throughout the entire cathode electrode andwherein a plurality of 3D networks of lithium ion- or sodiumion-conducting channels in the plurality of cathode particulates aremerged into one giant 3D network of lithium ion- or sodiumion-conducting channels substantially extended throughout the entirecathode electrode. A binder resin may be used to bond these cathodeparticulates together.

The method may further comprise combining an optional anode currentcollector, an anode electrode, a porous separator or solid-stateelectrolyte, the aforementioned cathode electrode, and an optionalcathode current collector to form an alkali metal battery. Optionally, aliquid electrolyte may be introduced into the battery cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) Schematic of a prior art lithium-ion battery cell (as anexample of an alkali metal battery) composed of an anode currentcollector, an anode electrode layer (e.g. thin Si coating layer), aporous separator, a cathode layer (e.g. sulfur layer), and a cathodecurrent collector.

FIG. 1(B) Schematic of a prior art lithium-ion battery cell (as anexample of an alkali metal battery), wherein the electrode layer iscomposed of discrete particles of an active material (e.g. graphite ortin oxide particles in the anode layer or LiCoO₂ in the cathode layer).

FIG. 1(C) Schematic of part of an internal structure of a prior artcylindrical lithium-ion battery cell, indicating the roll contains alaminated structure of an anode layer coated on an anode currentcollector, a porous separator, and a cathode layer coated on a cathodecurrent collector, which is wound to form a cylindrical roll.

FIG. 1(D) Schematic drawing of a presently invented anode particulate.

FIG. 1(E) Schematic drawing of an alkali metal battery containing anodeparticulates in the anode rod and cathode particulate in the cathodemass.

FIG. 1(F) Schematic of a presently invented cathode particulate.

FIG. 2 Schematic of a commonly used process for producing exfoliatedgraphite, expanded graphite flakes (thickness >100 nm), and graphenesheets (thickness <100 nm, more typically <10 nm, and can be as thin as0.34 nm).

FIG. 3 Ragone plots (gravimetric and volumetric power density vs. energydensity) of lithium-ion battery cells containing graphite particles asthe anode active material and carbon-coated LFP particles as the cathodeactive materials. Two of the 4 data curves are for the particulate-basedcells (containing presently invented anode particulates and cathodeparticulates) prepared according to an embodiment of instant inventionand the other two by the conventional slurry coating of electrodes(roll-coating).

FIG. 4 Ragone plots (both gravimetric and volumetric power density vs.gravimetric and volumetric energy density) of two cells, both containinggraphene-embraced Si nanoparticles as the anode active material andLiCoO₂ nanoparticles as the cathode active material. The experimentaldata were obtained from both the particulate-based Li-ion battery cells(containing extra discrete layers of electrolyte) and conventionalcells.

FIG. 5 Ragone plots of lithium metal batteries containing a lithium foilas the anode active material, dilithium rhodizonate (Li₂C₆O₆) as thecathode active material (formed into a cathode roll), and lithium salt(LiPF₆)—PC/DEC as organic liquid electrolyte. The data are for both theparticulate-based lithium metal cells prepared by the presently inventedmethod and those conventional cells by the conventional slurry coatingof electrodes.

FIG. 6 Ragone plots (gravimetric and volumetric power density vs. energydensity) of Na-ion battery cells containing hard carbon particles as theanode active material and carbon-coated Na₃V₂(PO₄)₂F₃ particles as thecathode active materials. Two of the 4 data curves are for the cellsprepared according to an embodiment of instant invention (containinganode particulates and cathode particulates of the instant invention)and the other two by the conventional slurry coating of electrodes(roll-coating).

FIG. 7 Ragone plots (both gravimetric and volumetric power density vs.gravimetric and volumetric energy density) of two cells, both containinggraphene-embraced Sn nanoparticles as the anode active material andNaFePO₄ nanoparticles as the cathode active material. The data are forboth sodium-ion cells prepared by the presently invented method andthose by the conventional slurry coating of electrodes.

FIG. 8 Ragone plots of sodium metal batteries containing agraphene-supported sodium foil as the anode active material, disodiumrhodizonate (Na₂C₆O₆) as the cathode active material, and sodium salt(NaPF₆)—PC/DEC as organic liquid electrolyte. The data are for bothsodium metal cells prepared by the presently invented method and thoseby the conventional slurry coating of electrodes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is directed at an alkali metal battery exhibiting anexceptionally high volumetric energy density and high gravimetric energydensity. This alkali metal battery can be a primary battery, but ispreferably a secondary battery selected from a lithium-ion battery or alithium metal secondary battery (e.g. using lithium metal as an anodeactive material), a sodium-ion battery, a sodium metal battery, apotassium-ion battery, or a potassium metal battery. The battery isbased on an aqueous electrolyte, a non-aqueous organic electrolyte, agel electrolyte, an ionic liquid electrolyte, a polymer electrolyte, asolid-state electrolyte, or a combination thereof. The final shape of analkali metal battery can be cylindrical, rectangular, cuboidal, etc. Thepresent invention is not limited to any battery shape or configuration.

In certain embodiments, the battery comprises (a) an anode having ananode active material, (b) a cathode containing a cathode activematerial, and (c) a separator-electrolyte layer, comprising a firstelectrolyte alone or a first electrolyte-porous separator assembly layer(e.g. a porous membrane wetted with a liquid or gel electrolyte or asolid-state electrolyte alone without an additional polymer membrane) inionic contact with the anode and the cathode.

The anode active material is in a form of multiple anode particulatesthat are packed together and possibly bonded together with a resinbinder. The individual particulate comprises: (i) an anode activematerial capable of reversibly absorbing and desorbing lithium ions orsodium ions, (ii) an electron-conducting material (e.g. a conductivepolymer, carbon nanotubes, carbon nanofibers, graphene sheets, etc.),and (iii) a lithium ion-conducting or sodium ion-conducting electrolyte,wherein the electron-conducting material forms a 3D network ofelectron-conducting pathways in electronic contact with the anode activematerial and the electrolyte forms a 3D network of lithium ion- orsodium ion-conducting channels in ionic contact with said anode activematerial. In certain embodiments, the anode active material occupies50-95% of the total anode particulate weight; the conductive materialoccupying 0.5 to 15% and the electrolyte typically 5-35% by weight.

As illustrated in FIG. 1(D) as a preferred embodiment, the anodeparticulate is composed of particles (e.g. 16) or fibrils of an anodeactive material, a conductive material (e.g. carbon nanofibers, 12, orgraphene sheets forming a 3D network of electron-conducting pathways),and a matrix of electrolyte, 14 (basically a 3D network ofion-conducting channels). The three components (active material,conductive material, and electrolyte) combined constitute an anodeparticulate which is in a solid or semi-solid state (having sufficientviscosity to maintain its shape during handling).

A very significant feature of the presently invented anode is the notionthat, when these multiple anode particulates are packed together to forman anode electrode, the 3D network of electron-conducting pathways inindividual anode particulates are merged into an extensive or large 3Dnetwork of electron-conducting pathways that can cover substantially theentire anode electrode. Further, when these multiple anode particulatesare packed together to form an anode electrode, the 3D network ofion-conducting channels in individual particulates are merged into anextensive or giant 3D network of lithium ion- or sodium ion-conductingchannels that can cover substantially the entire anode electrode. Assuch, the entire anode has a 3D network of electron-conducting pathwaysand a 3D network of lithium ion- or sodium ion-conducting channels thatare in contact with the anode active material. The giant 3D network ofelectron-conducting pathways is in electronic contact with an anodecurrent collector and/or a terminal tab that serves as a conduit throughwhich electrons can travel in and out of the entire anode.

It may be noted that the electrolyte in the anode particulate maycontain a lithium salt or sodium salt, a liquid medium (solvent, such asPC, DEC, and EC), and/or an ion-conducting polymer (e.g., PEG, PEO, PAN,etc.). Typically at least two of the three ingredients are included in aparticulate. The solvent may then be added to the electrode or cellafter the electrode or cell is made.

The invention also provides a lithium battery or sodium battery, whichcontains an optional anode current collector, the presently inventedanode containing anode particulates as defined above, a cathodecontaining a cathode active material, an optional cathode currentcollector, an electrolyte in ionic contact with the anode and thecathode, and an optional porous separator. This electrolyte can be thesame as or different than the electrolyte disposed in the individualanode particulates. Preferably, the cathode active material is also inthe presently invented particulate form.

Thus, in certain preferred embodiments (as illustrated in FIG. 1(F)),the cathode also contains multiple cathode particulates, wherein acathode particulate is composed of (i) a cathode active material (e.g.56) capable of reversibly absorbing and desorbing lithium ions or sodiumions, (ii) an electron-conducting material (e.g. a conductive polymer,carbon nanotubes 52, carbon nanofibers, graphene sheets, etc.), and(iii) a lithium ion-conducting or sodium ion-conducting electrolyte 54,wherein the electron-conducting material forms a 3D network ofelectron-conducting pathways in electronic contact with the cathodeactive material and the electrolyte forms a 3D network of lithium ion-or sodium ion-conducting channels in ionic contact with the cathodeactive material. The electrolyte in the cathode particulates can bedifferent than or the same as the electrolyte in the anode particulates.In certain embodiments, the cathode active material occupies 50-95% ofthe total cathode particulate weight; the conductive material occupying0.5 to 15% and the electrolyte typically 5-35% by weight.

When these multiple cathode particulates are packed together to form acathode electrode, the 3D network of electron-conducting pathways inindividual cathode particulates are merged into an extensive or giant 3Dnetwork of electron-conducting pathways that can cover substantially theentire cathode electrode. Further, when these multiple cathodeparticulates are packed together to form a cathode electrode, the 3Dnetwork of ion-conducting channels in individual cathode particulatesare merged into an extensive or giant 3D network of lithium ion- orsodium ion-conducting channels that can cover substantially the entirecathode electrode. As such, the entire cathode has a 3D network ofelectron-conducting pathways and a 3D network of lithium ion- or sodiumion-conducting channels that are in contact with the cathode activematerial. The giant 3D network of electron-conducting pathways is inelectronic contact with a cathode current collector and/or a terminaltab that serves as a conduit through which electrons can travel in andout of the entire cathode.

For convenience, we will use selected materials, such as lithium ironphosphate (LFP), vanadium oxide (V_(x)O_(y)), lithium nickel manganesecobalt oxide (NMC), dilithium rhodizonate (Li₂C₆O₆), and copperphthalocyanine (CuPc) as illustrative examples of the cathode activematerial, and graphite, SnO, Co₃O₄, and Si particles as examples of theanode active material. For sodium batteries, we will use selectedmaterials, such as NaFePO₄ and λ-MnO₂ particles, as illustrativeexamples of the cathode active material, and hard carbon and NaTi₂(PO₄)₃particles as examples of the anode active material of a Na-ion cell.Similar approaches are applicable to K-ion batteries. Nickel foam,graphite foam, graphene foam, and stainless steel fiber webs are used asexamples of conductive porous layers as intended current collectors.These should not be construed as limiting the scope of the invention.

As illustrated in FIG. 1(A), FIG. 1(B), and FIG. 1(C), a conventionallithium-ion battery cell is typically composed of an anode currentcollector (e.g. Cu foil), an anode electrode (anode active materiallayer) coated on the anode current collector, a porous separator and/oran electrolyte component, a cathode electrode (cathode active materiallayer) coated on the two primary surfaces of a cathode currentcollector, and a cathode current collector (e.g. Al foil). Although onlyone anode layer is shown, there can be two anode active material layerscoated on the two primary surfaces of the anode current collector.Similarly, there can be two cathode active material layers coated on thetwo primary surfaces of the cathode current collectors.

In a more commonly used cell configuration (FIG. 1(B)), the anode layeris composed of particles of an anode active material (e.g. graphite orSi), a conductive additive (e.g. carbon black particles), and a resinbinder (e.g. SBR or PVDF, not shown in the figure) that bonds the activematerial particles and the conductive additive together to form an anodelayer of structural integrity required for subsequent steps of batterycell production. The cathode layer is composed of particles of a cathodeactive material (e.g. LFP particles), a conductive additive (e.g. carbonblack particles), and a resin binder (e.g. PVDF).

Both the anode and the cathode layers are typically up to 100-200 μmthick to give rise to a presumably sufficient amount of current per unitfootprint electrode area. This thickness range is considered anindustry-accepted constraint under which a battery designer normallyworks under. This thickness constraint is due to several reasons: (a)the existing battery electrode coating machines are not equipped to coatexcessively thin or excessively thick electrode layers; (b) a thinnerlayer is preferred based on the consideration of reduced lithium iondiffusion path lengths; but, too thin a layer (e.g. <100 μm) does notcontain a sufficient amount of an active lithium storage material(hence, insufficient current output); (c) thicker electrodes are proneto delaminate or crack upon drying or handling after roll-coating; and(d) all non-active material layers in a battery cell (e.g. currentcollectors and separator) must be kept to a minimum in order to obtain aminimum overhead weight and a maximum lithium storage capability and,hence, a maximized energy density (Wk/kg or Wh/L of cell).

In a less commonly used cell configuration, as illustrated in FIG. 1(A),either the anode active material (e.g. Si or Li metal) or the cathodeactive material (e.g. lithium transition metal oxide) is deposited in athin film form directly onto a current collector, such as a sheet ofcopper foil or Al foil. However, such a thin film structure with anextremely small thickness-direction dimension (typically much smallerthan 500 nm, often necessarily thinner than 100 nm) implies that only asmall amount of active material can be incorporated in an electrode(given the same electrode or current collector surface area), providinga low total lithium storage capacity and low lithium storage capacityper unit electrode surface area. Such a thin film must have a thicknessless than 100 nm to be more resistant to cycling-induced cracking (forthe anode) or to facilitate a full utilization of the cathode activematerial. Such a constraint further diminishes the total lithium storagecapacity and the lithium storage capacity per unit electrode surfacearea. Such a thin-film battery has very limited scope of application.

On the anode side, a Si layer thicker than 100 nm has been found toexhibit poor cracking resistance during battery charge/discharge cycles.It takes but a few cycles for the electrode to get fragmented. On thecathode side, a sputtered layer of lithium metal oxide thicker than 100nm does not allow lithium ions to fully penetrate and reach full body ofthe cathode layer, resulting in a poor cathode active materialutilization rate. A desirable electrode thickness is at least 100 μm,with individual active material coating or particles having a dimensiondesirably less than 100 nm. Thus, these thin-film electrodes (with athickness <100 nm) directly deposited on a current collector fall shortof the required thickness by three (3) orders of magnitude. As a furtherproblem, all of the cathode active materials are not conductive to bothelectrons and lithium ions. A large layer thickness implies anexcessively high internal resistance and a poor active materialutilization rate.

In other words, there are several conflicting factors that must beconsidered concurrently when it comes to the design and selection of acathode or anode active material in terms of material type, size,electrode layer thickness, and active material mass loading. Thus far,there has been no effective solution offered by any prior art teachingto these often conflicting problems. We have solved these challengingissues, which have troubled battery designers and electrochemists alikefor more than 30 years, by developing a new form of anode materials anda new form of cathode material that enable the production of a alkalimetal battery without the aforementioned issues. The invention alsoprovides processes for producing anode particulate, cathodeparticulates, the anode, the cathode, and such a battery.

The prior art lithium battery cell is typically made by a process thatincludes the following steps: (a) The first step includes mixingparticles of the anode active material (e.g. Si nanoparticles ormesocarbon microbeads, MCMBs), a conductive filler (e.g. graphiteflakes), a resin binder (e.g. PVDF) in a solvent (e.g. NMP) to form ananode slurry. On a separate basis, particles of the cathode activematerial (e.g. LFP particles), a conductive filler (e.g. acetyleneblack), a resin binder (e.g. PVDF) are mixed and dispersed in a solvent(e.g. NMP) to form a cathode slurry. (b) The second step includescoating the anode slurry onto one or both primary surfaces of an anodecurrent collector (e.g. Cu foil), drying the coated layer by vaporizingthe solvent (e.g. NMP) to form a dried anode electrode coated on Cufoil. Similarly, the cathode slurry is coated and dried to form a driedcathode electrode coated on Al foil. Slurry coating is normally done ina roll-to-roll manner in a real manufacturing situation; (c) The thirdstep includes laminating an anode/Cu foil sheet, a porous separatorlayer, and a cathode/Al foil sheet together to form a 3-layer or 5-layerassembly, which is cut and slit into desired sizes and stacked to form arectangular structure (as an example of shape) or rolled into acylindrical cell structure. (d) The rectangular or cylindrical laminatedstructure is then encased in an aluminum-plastic laminated envelope orsteel casing. (e) A liquid electrolyte is then injected into thelaminated structure to make a lithium battery cell.

There are several serious problems associated with the conventionalprocess and the resulting lithium-ion battery cell or sodium-ion cell:

-   -   1) It is very difficult to produce an electrode layer (anode        layer or cathode layer) that is thicker than 200 μm (100 μm on        each side of a solid current collector, such as Al foil) and,        thus, there is limited amount of active materials that can be        included in a unit battery cell. There are several reasons why        this is the case. An electrode of 100-200 μm in thickness        typically requires a heating zone of 30-50 meters long in a        slurry coating facility, which is too time consuming, too energy        intensive, and not cost-effective. For some electrode active        materials, such as metal oxide particles, it has not been        possible to produce an electrode of good structural integrity        that is thicker than 100 μm in a real manufacturing environment        on a continuous basis. The resulting electrodes are very fragile        and brittle. Thicker electrodes have a high tendency to        delaminate and crack.    -   2) With a conventional process, as depicted in FIG. 1(A), the        actual mass loadings of the electrodes and the apparent        densities for the active materials are too low to achieve a        gravimetric energy density of >200 Wh/kg. In most cases, the        anode active material mass loading of the electrodes (areal        density) is significantly lower than 25 mg/cm² and the apparent        volume density or tap density of the active material is        typically less than 1.2 g/cm³ even for relatively large        particles of graphite. The cathode active material mass loading        of the electrodes (areal density) is significantly lower than 45        mg/cm² for lithium metal oxide-type inorganic materials and        lower than 15 mg/cm² for organic or polymer materials. In        addition, there are so many other non-active materials (e.g.        conductive additive and resin binder) that add additional        weights and volumes to the electrode without contributing to the        cell capacity. These low areal densities and low volume        densities result in relatively low gravimetric energy density        and low volumetric energy density.    -   3) The conventional process requires dispersing electrode active        materials (anode active material or cathode active material) in        a liquid solvent (e.g. NMP) to make a slurry and, upon coating        on a current collector surface, the liquid solvent has to be        removed to dry the electrode layer. Once the anode and cathode        layers, along with a separator layer, are laminated together and        packaged in a housing to make a supercapacitor cell, one then        injects a liquid electrolyte into the cell. In actuality, one        makes the two electrodes wet, then makes the electrodes dry, and        finally makes them wet again. Such a wet-dry-wet process does        not sound like a good process at all. Furthermore, NMP is a        highly regulated solvent and must be handled with care and        additional equipment is required to capture the vaporized NMP        for re-use. Solvent recycling equipment is typically very        expensive.    -   4) Current lithium-ion batteries still suffer from a relatively        low gravimetric energy density and low volumetric energy        density. Commercially available lithium-ion batteries exhibit a        gravimetric energy density of approximately 150-220 Wh/kg and a        volumetric energy density of 450-600 Wh/L.

In literature, the energy density data reported based on either theactive material weight alone or the electrode weight cannot directlytranslate into the energy densities of a practical battery cell ordevice. The “overhead weight” or weights of other device components(binder, conductive additive, current collectors, separator,electrolyte, and packaging) must also be taken into account. Theconvention production process results in the weight proportion of theanode active material (e.g. graphite or carbon) in a lithium-ion batterybeing typically from 12% to 17%, and that of the cathode active material(e.g. LiMn₂O₄) from 20% to 35%.

Schematically shown in FIG. 1(C) is part of an internal structure of aprior art cylindrical lithium-ion battery cell, indicating that eachbattery cell contains a roll, which is composed of a laminate of ananode layer 110 coated on an anode current collector 108, a porousseparator 112, and a cathode layer 114 coated on a cathode currentcollector 116.

The presently invented anode particulates (as schematically illustratedin FIG. 1(D)) and the cathode particulates (as schematically illustratedin FIG. 1(F)) each already have the three necessary ingredients (anactive material, an electron-conducting additive, and an ion-conductingmatrix (electrolyte) to function as an electrode. Such a feature enablesa lithium-ion or sodium-ion battery cell to be produced using a widevariety of highly cost-effective and elegantly simple methods. Thesemethods can eliminate the shortcomings of the conventional processes andresulting batteries. The resulting battery cell can be in any geometricshape or dimensions.

As an example, a simple and easy-to-make battery cell configuration isillustrated in FIG. 1(E). The cell contains a chamber 30 thataccommodates a mass of multiple cathode particulates, which are inelectronic contact with a cathode current collector 40 at the bottom ofthe chamber. A cylindrical bar 20 composed of anode particulates wrappedaround by a porous membrane 24 is inserted into the chamber 30. Themembrane serves as a separator that electronically isolates the anodefrom the cathode, but is permeable to lithium or sodium ions. There canbe multiple anode bars like 20 that are inserted into the mass ofcathode particulates in the chamber. For each anode bar, there can be ananode current collector (e.g. Cu wire, 26) inserted into the anode barand in electronic contact with the giant 3D network ofelectron-conducting pathways. Further, instead of a plate-like cathodecurrent collector (e.g. 40), one may choose to implement a plurality ofAl wires into the mass of the cathode particulates contained insidechamber 30.

Most significantly, the presently invented anode particulates andcathode particulates make it possible to avoid the problems associatedwith the conventional slurry coating process for manufacturing currentlithium-ion or sodium-ion batteries: the use of undesirable solvents(e.g. NMP), difficulty in producing thicker electrodes, low areal massdensity of active materials, and significantly lower energy density thanis otherwise possible. The invention also makes it possible to developand implement technically feasible and economically viable processes.

The electron-conducting material may be selected from intrinsicallyconducting polymer chains, metal nanowires, conductive polymernanofibers, conductive polymer-coated fibers, carbon nanofibers, carbonnanotubes, graphene sheets, expanded graphite platelets, carbon fibers,graphite fibers, needle coke, carbon black particles, or a combinationthereof.

Additionally, in each anode electrode or cathode electrode, allelectrode active material particles are pre-dispersed in or mixed withan electrolyte (no electrolyte non-wettability or inaccessibilityissues), eliminating the existence of dry pockets commonly present in anelectrode prepared by the conventional process of wet coating, drying,packing, and electrolyte injection.

In a preferred embodiment, the anode active material is a prelithiatedor pre-sodiated version of graphene sheets selected from pristinegraphene, graphene oxide, reduced graphene oxide, graphene fluoride,graphene chloride, graphene bromide, graphene iodide, hydrogenatedgraphene, nitrogenated graphene, chemically functionalized graphene, ora combination thereof. The starting graphitic material for producing anyone of the above graphene materials may be selected from naturalgraphite, artificial graphite, mesophase carbon, mesophase pitch,mesocarbon microbead, soft carbon, hard carbon, coke, carbon fiber,carbon nanofiber, carbon nanotube, or a combination thereof. Graphenematerials are also a good conductive additive for both the anode andcathode active materials of an alkali metal battery.

For the purpose of defining the claims of the instant application, NGPsor graphene materials include single-layer graphene, multi-layer layergraphene, pristine graphene, graphene oxide, reduced graphene oxide(RGO), graphene fluoride, graphene chloride, graphene bromide, grapheneiodide, hydrogenated graphene, nitrogenated graphene, chemicallyfunctionalized graphene, doped graphene (e.g. doped by B or N). Theconstituent graphene planes of a graphite crystallite in a natural orartificial graphite particle can be exfoliated and extracted or isolatedto obtain individual graphene sheets of hexagonal carbon atoms, whichare single-atom thick, provided the inter-planar van der Waals forcescan be overcome. An isolated, individual graphene plane of carbon atomsis commonly referred to as single-layer graphene. A stack of multiplegraphene planes bonded through van der Waals forces in the thicknessdirection with an inter-graphene plane spacing of approximately 0.3354nm is commonly referred to as a multi-layer graphene. A multi-layergraphene platelet has up to 300 layers of graphene planes (<100 nm inthickness), but more typically up to 30 graphene planes (<10 nm inthickness), even more typically up to 20 graphene planes (<7 nm inthickness), and most typically 2-10 graphene planes (commonly referredto as few-layer graphene).

The term “pristine graphene” encompasses a graphene material havingessentially zero % (less than 0.01%) of non-carbon elements. The term“non-pristine graphene” encompasses graphene material having 0.01% to50% by weight of non-carbon elements, preferably <5% by weight. The term“doped graphene” encompasses graphene material having less than 10% of anon-carbon element. This non-carbon element can include hydrogen,oxygen, nitrogen, magnesium, iron, sulfur, fluorine, bromine, iodine,boron, phosphorus, sodium, and combinations thereof. Graphene oxide(including RGO) can have 0.01%-50% by weight of oxygen. Reduced grapheneoxide typically has an oxygen content of 0.01%-5% by weight.

Single-layer graphene and multi-layer graphene sheets are collectivelycalled “nano graphene platelets” (NGPs). Graphene sheets/platelets(collectively, NGPs) are a class of carbon nanomaterial (essentially twodimensional nano carbon) that is distinct from essentially zerodimensional fullerene, essentially one dimensional CNT and CNF, and thethree dimensional graphite. For the purpose of defining the claims andas is commonly understood in the art, a graphene material (isolatedgraphene sheets) is not (and does not include) a carbon nanotube (CNT)or a carbon nanofiber (CNF).

In one process, graphene materials are obtained by intercalating naturalgraphite particles with a strong acid and/or an oxidizing agent toobtain a graphite intercalation compound (GIC) or graphite oxide (GO),as illustrated in FIG. 2. The presence of chemical species or functionalgroups in the interstitial spaces between graphene planes in a GIC or GOserves to increase the inter-graphene spacing (d₀₀₂, as determined byX-ray diffraction), thereby significantly reducing the van der Waalsforces that otherwise hold graphene planes together along the c-axisdirection. The GIC or GO is most often produced by immersing naturalgraphite powder in a mixture of sulfuric acid, nitric acid (an oxidizingagent), and another oxidizing agent (e.g. potassium permanganate orsodium perchlorate). The resulting GIC is actually some type of graphiteoxide (GO) particles if an oxidizing agent is present during theintercalation procedure. This GIC or GO is then repeatedly washed andrinsed in water to remove excess acids, resulting in a graphite oxidesuspension or dispersion, which contains discrete and visuallydiscernible graphite oxide particles dispersed in water. In order toproduce graphene materials, one can follow one of the two processingroutes after this rinsing step, briefly described below:

Route 1 involves removing water from the suspension to obtain“expandable graphite,” which is essentially a mass of dried GIC or driedgraphite oxide particles. Upon exposure of expandable graphite to atemperature in the range of typically 800-1,050° C. for approximately 30seconds to 2 minutes, the GIC undergoes a rapid volume expansion by afactor of 30-300 to form “graphite worms”, which are each a collectionof exfoliated, but largely un-separated graphite flakes that remaininterconnected.

The exfoliated graphite is subjected to high-intensity mechanicalshearing (e.g. using an ultrasonicator, high-shear mixer, high-intensityair jet mill, or high-energy ball mill) to form separated single-layerand multi-layer graphene sheets (collectively called NGPs), as disclosedin our U.S. application Ser. No. 10/858,814 (Jun. 3, 2004) (now U.S.Patent Publication No. 2005-0271574). Single-layer graphene can be asthin as 0.34 nm, while multi-layer graphene can have a thickness up to100 nm, but more typically less than 10 nm (commonly referred to asfew-layer graphene). Multiple graphene sheets or platelets may be madeinto a sheet of NGP paper using a paper-making process. This sheet ofNGP paper is an example of the porous graphene structure layer utilizedin the presently invented process.

Route 2 entails ultrasonicating the graphite oxide suspension (e.g.graphite oxide particles dispersed in water) for the purpose ofseparating/isolating individual graphene oxide sheets from graphiteoxide particles. This is based on the notion that the inter-grapheneplane separation has been increased from 0.3354 nm in natural graphiteto 0.6-1.1 nm in highly oxidized graphite oxide, significantly weakeningthe van der Waals forces that hold neighboring planes together.Ultrasonic power can be sufficient to further separate graphene planesheets to form fully separated, isolated, or discrete graphene oxide(GO) sheets. These graphene oxide sheets can then be chemically orthermally reduced to obtain “reduced graphene oxides” (RGO) typicallyhaving an oxygen content of 0.001%-10% by weight, more typically0.01%-5% by weight, most typically and preferably less than 2% by weightof oxygen.

Pristine graphene, in smaller discrete graphene sheets (typically 0.3 μmto 10 μm), may be produced by one of the following three processes: (A)intercalating the graphitic material with a non-oxidizing agent,followed by a thermal or chemical exfoliation treatment in anon-oxidizing environment; (B) subjecting the graphitic material to asupercritical fluid environment for inter-graphene layer penetration andexfoliation; or (C) dispersing the graphitic material in a powder formto an aqueous solution containing a surfactant or dispersing agent toobtain a suspension and subjecting the suspension to directultrasonication to obtain a graphene dispersion.

In Procedure (A), a particularly preferred step comprises (i)intercalating the graphitic material with a non-oxidizing agent,selected from an alkali metal (e.g., potassium, sodium, lithium, orcesium), alkaline earth metal, or an alloy, mixture, or eutectic of analkali or alkaline metal; and (ii) a chemical exfoliation treatment(e.g., by immersing potassium-intercalated graphite in ethanolsolution).

In Procedure (B), a preferred step comprises immersing the graphiticmaterial to a supercritical fluid, such as carbon dioxide (e.g., attemperature T>31° C. and pressure P>7.4 MPa) and water (e.g., at T>374°C. and P>22.1 MPa), for a period of time sufficient for inter-graphenelayer penetration (tentative intercalation). This step is then followedby a sudden de-pressurization to exfoliate individual graphene layers.Other suitable supercritical fluids include methane, ethane, ethylene,hydrogen peroxide, ozone, water oxidation (water containing a highconcentration of dissolved oxygen), or a mixture thereof.

In Procedure (C), a preferred step comprises (a) dispersing particles ofa graphitic material in a liquid medium containing therein a surfactantor dispersing agent to obtain a suspension or slurry; and (b) exposingthe suspension or slurry to ultrasonic waves (a process commonlyreferred to as ultrasonication) at an energy level for a sufficientlength of time to produce a graphene dispersion of separated graphenesheets (non-oxidized NGPs) dispersed in a liquid medium (e.g. water,alcohol, or organic solvent).

The graphene oxide (GO) may be obtained by immersing powders orfilaments of a starting graphitic material (e.g. natural graphitepowder) in an oxidizing liquid medium (e.g. a mixture of sulfuric acid,nitric acid, and potassium permanganate) in a reaction vessel at adesired temperature for a period of time (typically from 0.5 to 96hours, depending upon the nature of the starting material and the typeof oxidizing agent used). As previously described above, the resultinggraphite oxide particles may then be subjected to thermal exfoliation orultrasonic wave-induced exfoliation to produce isolated GO sheets. TheseGO sheets can then be converted into various graphene materials bysubstituting —OH groups with other chemical groups (e.g. —Br, NH₂,etc.).

Fluorinated graphene or graphene fluoride is herein used as an exampleof the halogenated graphene material group. There are two differentapproaches that have been followed to produce fluorinated graphene: (1)fluorination of pre-synthesized graphene: This approach entails treatinggraphene prepared by mechanical exfoliation or by CVD growth withfluorinating agent such as XeF₂, or F-based plasmas; (2) Exfoliation ofmultilayered graphite fluorides: Both mechanical exfoliation and liquidphase exfoliation of graphite fluoride can be readily accomplished.

Interaction of F₂ with graphite at high temperature leads to covalentgraphite fluorides (CF)_(n) or (C₂F)_(n) while at low temperaturesgraphite intercalation compounds (GIC) C_(x)F (2≤x≤24) form. In (CF)_(n)carbon atoms are sp3-hybridized and thus the fluorocarbon layers arecorrugated consisting of trans-linked cyclohexane chairs. In (C₂F)_(n)only half of the C atoms are fluorinated and every pair of the adjacentcarbon sheets are linked together by covalent C—C bonds. Systematicstudies on the fluorination reaction showed that the resulting F/C ratiois largely dependent on the fluorination temperature, the partialpressure of the fluorine in the fluorinating gas, and physicalcharacteristics of the graphite precursor, including the degree ofgraphitization, particle size, and specific surface area. In addition tofluorine (F₂), other fluorinating agents may be used, although most ofthe available literature involves fluorination with F₂ gas, sometimes inpresence of fluorides.

For exfoliating a layered precursor material to the state of individuallayers or few-layers, it is necessary to overcome the attractive forcesbetween adjacent layers and to further stabilize the layers. This may beachieved by either covalent modification of the graphene surface byfunctional groups or by non-covalent modification using specificsolvents, surfactants, polymers, or donor-acceptor aromatic molecules.The process of liquid phase exfoliation includes ultrasonic treatment ofa graphite fluoride in a liquid medium.

The nitrogenation of graphene can be conducted by exposing a graphenematerial, such as graphene oxide, to ammonia at high temperatures(200-400° C.). Nitrogenated graphene could also be formed at lowertemperatures by a hydrothermal method; e.g. by sealing GO and ammonia inan autoclave and then increased the temperature to 150-250° C. Othermethods to synthesize nitrogen doped graphene include nitrogen plasmatreatment on graphene, arc-discharge between graphite electrodes in thepresence of ammonia, ammonolysis of graphene oxide under CVD conditions,and hydrothermal treatment of graphene oxide and urea at differenttemperatures.

There is no restriction on the types of anode active materials orcathode active materials that can be used in practicing the instantinvention. In one preferred embodiment, the anode active material in theinvented anode particulate is selected from the group consisting of: (a)Particles of natural graphite, artificial graphite, mesocarbonmicrobeads (MCMB), and carbon (including soft carbon, hard carbon,carbon nanofiber, and carbon nanotube); (b) silicon (Si), germanium(Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn),aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti),iron (Fe), and cadmium (Cd); (Si, Ge, Al, and Sn are most desirable dueto their high specific capacities.) (c) alloys or intermetalliccompounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, or Cd with other elements,wherein the alloys or compounds are stoichiometric or non-stoichiometric(e.g. SiAl, SiSn); (d) oxides, carbides, nitrides, sulfides, phosphides,selenides, and tellurides of Si, Ge, Sn, Nb, Mo, Pb, Sb, Bi, Zn, Al, Fe,Ni, Co, Ti, Mn, or Cd, and their mixtures or composites (e.g. SnO, TiO₂,Li₄Ti₅O₁₂, Co₃O₄, TiNb₂O₇, etc.); (e) prelithiated versions thereof(e.g. prelithiated TiO₂, which is lithium titanate); (f) prelithiatedgraphene sheets; and combinations thereof.

In another preferred embodiment, the anode active material in the anodeparticulate is a pre-sodiated or pre-potassiated version of graphenesheets selected from pristine graphene, graphene oxide, reduced grapheneoxide, graphene fluoride, graphene chloride, graphene bromide, grapheneiodide, hydrogenated graphene, nitrogenated graphene, chemicallyfunctionalized graphene, or a combination thereof. The startinggraphitic material for producing any one of the above graphene materialsmay be selected from natural graphite, artificial graphite, mesophasecarbon, mesophase pitch, mesocarbon microbead, soft carbon, hard carbon,coke, carbon fiber, carbon nanofiber, carbon nanotube, or a combinationthereof. Graphene materials are also a good conductive additive for boththe anode and cathode active materials of an alkali metal battery.

Particularly desired is an anode active material that contains an alkaliintercalation compound selected from petroleum coke, carbon black,amorphous carbon, hard carbon, templated carbon, hollow carbonnanowires, hollow carbon sphere, titanates, NaTi₂(PO₄)₃, Na₂Ti₃O₇(Sodium titanate), Na₂C₈H₄O₄ (Disodium Terephthalate), Na₂TP (SodiumTerephthalate), TiO₂, Na_(x)TiO₂ (0.2≤x≤1.0), carboxylate basedmaterials, C₈H₄Na₂O₄, C₈H₆O₄, C₈H₅NaO₄, C₈Na₂F₄O₄, C₁₀H₂Na₄O₈, C₁₄H₄O₆,C₁₄H₄Na₄O₈, or a combination thereof.

In an embodiment, the anode may contain a mixture of 2 or 3 types ofanode active materials (e.g. mixed particles of activatedcarbon+NaTi₂(PO₄)₃) and the cathode can be a sodium intercalationcompound alone (e.g. Na_(x)MnO₂), an electric double layercapacitor-type cathode active material alone (e.g. activated carbon), aredox pair of λ-MnO₂/activated carbon for pseudo-capacitance.

A wide variety of cathode active materials can be used to practice thepresently invented process. The cathode active material typically is analkali metal intercalation compound or alkali metal-absorbing compoundthat is capable of storing alkali metal ions when the battery isdischarged and releasing alkali metal ions into the electrolyte whenrec-charged. The cathode active material may be selected from aninorganic material, an organic or polymeric material, a metaloxide/phosphate/sulfide (most desired types of inorganic cathodematerials), or a combination thereof. Preferably, the cathode activematerials are also in a particulate form containing all the threeingredients (cathode active material, 3D conducting network, andelectrolyte species) in a particulate.

The group of metal oxide, metal phosphate, and metal sulfides consistingof lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide,lithium vanadium oxide, lithium transition metal oxide, lithium-mixedmetal oxide, lithium iron phosphate, lithium manganese phosphate,lithium vanadium phosphate, lithium mixed metal phosphates, transitionmetal sulfides, and combinations thereof. In particular, the lithiumvanadium oxide may be selected from the group consisting of VO₂,Li_(x)VO₂, V₂O₅, Li_(x)V₂O₅, V₃O₈, Li_(x)V₃O₈, Li_(x)V₃O₇, V₄O₉,Li_(x)V₄O₉, V₆O₁₃, Li₈V₆O₁₃, their doped versions, their derivatives,and combinations thereof, wherein 0.1<x<5. Lithium transition metaloxide may be selected from a layered compound LiMO₂, spinel compoundLiM₂O₄, olivine compound LiMPO₄, silicate compound Li₂MSiO₄, Tavoritecompound LiMPO₄F, borate compound LiMBO₃, or a combination thereof,wherein M is a transition metal or a mixture of multiple transitionmetals.

In the alkali metal cell or alkali metal-ion cell, the cathode activematerial may contain a sodium intercalation compound (or their potassiumcounterparts) selected from NaFePO₄ (Sodium iron phosphate),Na_(0.7)FePO₄, Na_(1.5) VOPO₄F_(0.5), Na₃V₂(PO₄)₃, Na₃V₂(PO₄)₂F₃,Na₂FePO₄F, NaFeF₃, NaVPO₄F, Na₃V₂(PO₄)₂F₃, Na_(1.5)VOPO₄F_(0.5),Na₃V₂(PO₄)₃, NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅, Na_(x)CoO₂ (Sodiumcobalt oxide), Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂, Na_(x)(Fe_(1/2)Mn_(1/2))O₂,Na_(x)MnO₂ (Sodium manganese bronze), λ-MnO₂, Na_(0.44)MnO₂,Na_(0.44)MnO₂/C, Na₄Mn₉O₁₈, NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇,Ni_(1/3)Mn_(1.3)Co_(1/3)O₂, Cu_(0.56)Ni_(0.44)HCF (Copper and nickelhexacyanoferrate), NiHCF (nickel hexacyanoferrate), Na_(x)CoO₂, NaCrO₂,Na₃Ti₂(PO₄)₃, NiCo₂O₄, Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C,NaV_(1-x)Cr_(x)PO₄F, Se_(y)S_(z) (Selenium and Selenium/Sulfur, z/y from0.01 to 100), Se (without S), Alluaudites, or a combination thereof.

Other inorganic materials for use as a cathode active material may beselected from sulfur, sulfur compound, lithium polysulfide, transitionmetal dichalcogenide, a transition metal trichalcogenide, or acombination thereof. In particular, the inorganic material is selectedfrom TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, CoO₂, an iron oxide, a vanadiumoxide, or a combination thereof. These will be further discussed later.

In particular, the inorganic material may be selected from: (a) bismuthselenide or bismuth telluride, (b) transition metal dichalcogenide ortrichalcogenide, (c) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (d) boron nitride, or(e) a combination thereof.

Alternatively, the cathode active material may be selected from afunctional material or nanostructured material having an alkali metalion-capturing functional group or alkali metal ion-storing surface indirect contact with the electrolyte. Preferably, the functional groupreversibly reacts with an alkali metal ion, forms a redox pair with analkali metal ion, or forms a chemical complex with an alkali metal ion.The functional material or nanostructured material may be selected fromthe group consisting of (a) a nanostructured or porous disordered carbonmaterial selected from a soft carbon, hard carbon, polymeric carbon orcarbonized resin, mesophase carbon, coke, carbonized pitch, carbonblack, activated carbon, nanocellular carbon foam or partiallygraphitized carbon; (b) a nano graphene platelet selected from asingle-layer graphene sheet or multi-layer graphene platelet; (c) acarbon nanotube selected from a single-walled carbon nanotube ormulti-walled carbon nanotube; (d) a carbon nanofiber, nanowire, metaloxide nanowire or fiber, conductive polymer nanofiber, or a combinationthereof; (e) a carbonyl-containing organic or polymeric molecule; (f) afunctional material containing a carbonyl, carboxylic, or amine group;and combinations thereof.

The functional material or nanostructured material may be selected fromthe group consisting ofPoly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene), Na_(x)C₆O₆ (x=1-3),Na₂(C₆H₂O₄), Na₂C₈H₄O₄ (Na terephthalate), Na₂C₆H₄O₄(Litrans-trans-muconate), 3,4,9,10-perylenetetracarboxylicacid-dianhydride(PTCDA) sulfide polymer, PTCDA,1,4,5,8-naphthalene-tetracarboxylicacid-dianhydride (NTCDA),Benzene-1,2,4,5-tetracarboxylic dianhydride, 1,4,5,8-tetrahydroxyanthraquinon, Tetrahydroxy-p-benzoquinone, and combinations thereof.Desirably, the functional material or nanostructured material has afunctional group selected from —COOH, ═O, —NH₂, —OR, or —COOR, where Ris a hydrocarbon radical.

The organic material or polymeric material may be selected fromPoly(anthraquinonyl sulfide) (PAQS), a lithium oxocarbon,3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, Quino(triazene), redox-active organic material,Tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxyanthraquinone) (PADAQ), phosphazene disulfide polymer ([(NPS₂)₃]n),lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer,Hexaazatrinaphtylene (HATN), Hexaazatriphenylene hexacarbonitrile(HAT(CN)₆), 5-Benzylidene hydantoin, Isatine lithium salt, Pyromelliticdiimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi₄),N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAM), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.

The thioether polymer is selected fromPoly[methanetetryl-tetra(thiomethylene)] (PMTTM),Poly(2,4-dithiopentanylene) (PDTP), a polymer containingPoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, Poly(2-phenyl-1,3-dithiolane) (PPDT),Poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT),poly[1,2,4,5-tetrakis(propylthio)benzene] (PTKPTB, orpoly[3,4(ethylenedithio)thiophene] (PEDTT).

The organic material may be selected from a phthalocyanine compoundselected from copper phthalocyanine, zinc phthalocyanine, tinphthalocyanine, iron phthalocyanine, lead phthalocyanine, nickelphthalocyanine, vanadyl phthalocyanine, fluorochromium phthalocyanine,magnesium phthalocyanine, manganous phthalocyanine, dilithiumphthalocyanine, aluminum phthalocyanine chloride, cadmiumphthalocyanine, chlorogallium phthalocyanine, cobalt phthalocyanine,silver phthalocyanine, a metal-free phthalocyanine, a chemicalderivative thereof, or a combination thereof.

The lithium intercalation compound or lithium-absorbing compound may beselected from a metal carbide, metal nitride, metal boride, metaldichalcogenide, or a combination thereof. Preferably, the lithiumintercalation compound or lithium-absorbing compound is selected from anoxide, dichalcogenide, trichalcogenide, sulfide, selenide, or tellurideof niobium, zirconium, molybdenum, hafnium, tantalum, tungsten,titanium, vanadium, chromium, cobalt, manganese, iron, or nickel in ananowire, nanodisc, nanoribbon, or nanoplatelet form.

We have discovered that a wide variety of two-dimensional (2D) inorganicmaterials can be used as a cathode active material in the presentedinvented lithium battery prepared by the invented direct activematerial-electrolyte injection process. Layered materials represent adiverse source of 2D systems that can exhibit unexpected electronicproperties and good affinity to lithium ions. Although graphite is thebest known layered material, transition metal dichalcogenides (TMDs),transition metal oxides (TMOs), and a broad array of other compounds,such as BN, Bi₂Te₃, and Bi₂Se₃, are also potential sources of 2Dmaterials.

Preferably, the lithium intercalation compound or lithium-absorbingcompound is selected from nanodiscs, nanoplatelets, nanocoating, ornanosheets of an inorganic material selected from: (a) bismuth selenideor bismuth telluride, (b) transition metal dichalcogenide ortrichalcogenide, (c) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (d) boron nitride, or(e) a combination thereof; wherein the discs, platelets, or sheets havea thickness less than 100 nm. The lithium intercalation compound orlithium-absorbing compound may contain nanodiscs, nanoplatelets,nanocoating, or nanosheets of a compound selected from: (i) bismuthselenide or bismuth telluride, (ii) transition metal dichalcogenide ortrichalcogenide, (iii) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (iv) boron nitride, or(v) a combination thereof, wherein the discs, platelets, coating, orsheets have a thickness less than 100 nm.

Non-graphene 2D nanomaterials, single-layer or few-layer (up to 20layers), can be produced by several methods: mechanical cleavage, laserablation (e.g. using laser pulses to ablate TMDs down to a singlelayer), liquid phase exfoliation, and synthesis by thin film techniques,such as PVD (e.g. sputtering), evaporation, vapor phase epitaxy, liquidphase epitaxy, chemical vapor epitaxy, molecular beam epitaxy (MBE),atomic layer epitaxy (ALE), and their plasma-assisted versions.

A wide range of electrolytes can be used for practicing the instantinvention. Most preferred are non-aqueous organic and/or ionic liquidelectrolytes, along with a polymer or an inorganic solid-stateelectrolyte, in the anode particulate or the cathode particulate. Foruse between the anode and the cathode, solid state electrolyte ispreferred.

The non-aqueous electrolyte to be employed herein may be produced bydissolving an electrolytic salt in a non-aqueous solvent. Any knownnon-aqueous solvent which has been employed as a solvent for a lithiumsecondary battery can be employed. The organic solvent may contain aliquid solvent selected from the group consisting of 1,3-dioxolane(DOL), 1,2-dimethoxyethane (DME), tetraethylene glycol dimethylether(TEGDME), poly(ethylene glycol) dimethyl ether (PEGDME), diethyleneglycol dibutyl ether (DEGDBE), 2-ethoxyethyl ether (EEE), sulfone,sulfolane, ethylene carbonate (EC), dimethyl carbonate (DMC),methylethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate,methyl propionate, propylene carbonate (PC), gamma-butyrolactone (γ-BL),acetonitrile (AN), ethyl acetate (EA), propyl formate (PF), methylformate (MF), toluene, xylene, methyl acetate (MA), fluoroethylenecarbonate (FEC), vinylene carbonate (VC), allyl ethyl carbonate (AEC), ahydrofloroether (e.g. methyl perfluorobutyl ether, MFE, or ethylperfluorobutyl ether, EFE), and combinations thereof.

Examples of preferred mixed solvent are a composition comprising EC andMEC; comprising EC, PC and MEC; comprising EC, MEC and DEC; comprisingEC, MEC and DMC; and comprising EC, MEC, PC and DEC; with the volumeratio of MEC being controlled within the range of 30 to 80%. Byselecting the volume ratio of MEC from the range of 30 to 80%, morepreferably 40 to 70%, the conductivity of the solvent can be improved.With the purpose of suppressing the decomposition reaction of thesolvent, an electrolyte having carbon dioxide dissolved therein may beemployed, thereby effectively improving both the capacity and cycle lifeof the battery. The electrolytic salts to be incorporated into anon-aqueous electrolyte may be selected from a lithium salt such aslithium perchlorate (LiClO₄), lithium hexafluorophosphate (LiPF₆),lithium borofluoride (LiBF₄), lithium hexafluoroarsenide (LiAsF₆),lithium trifluoro-metasulfonate (LiCF₃SO₃) and bis-trifluoromethylsulfonylimide lithium [LiN(CF₃SO₂)₂]. Among them, LiPF₆, LiBF₄ andLiN(CF₃SO₂)₂ are preferred. The content of aforementioned electrolyticsalts in the non-aqueous solvent is preferably 0.5 to 2.0 mol/l.

For use in a sodium cell or potassium cell, the organic electrolyte maycontain an alkali metal salt preferably selected from sodium perchlorate(NaClO₄), potassium perchlorate (KClO₄), sodium hexafluorophosphate(NaPF₆), potassium hexafluorophosphate (KPF₆), sodium borofluoride(NaBF₄), potassium borofluoride (KBF₄), sodium hexafluoroarsenide,potassium hexafluoroarsenide, sodium trifluoro-metasulfonate (NaCF₃SO₃),potassium trifluoro-metasulfonate (KCF₃SO₃), bis-trifluoromethylsulfonylimide sodium (NaN(CF₃SO₂)₂), bis-trifluoromethyl sulfonylimidepotassium (KN(CF₃SO₂)₂), an ionic liquid salt, or a combination thereof.

The ionic liquid is composed of ions only. Ionic liquids are low meltingtemperature salts that are in a molten or liquid state when above adesired temperature. For instance, a salt is considered as an ionicliquid if its melting point is below 100° C. If the melting temperatureis equal to or lower than room temperature (25° C.), the salt isreferred to as a room temperature ionic liquid (RTIL). The IL salts arecharacterized by weak interactions, due to the combination of a largecation and a charge-delocalized anion. This results in a low tendency tocrystallize due to flexibility (anion) and asymmetry (cation).

A typical and well-known ionic liquid is formed by the combination of a1-ethyl-3-methylimidazolium (EMI) cation and anN,N-bis(trifluoromethane)sulphonamide (TFSI) anion. This combinationgives a fluid with an ionic conductivity comparable to many organicelectrolyte solutions and a low decomposition propensity and low vaporpressure up to ˜300-400° C. This implies a generally low volatility andnon-flammability and, hence, a much safer electrolyte for batteries.

Ionic liquids are basically composed of organic ions that come in anessentially unlimited number of structural variations owing to thepreparation ease of a large variety of their components. Thus, variouskinds of salts can be used to design the ionic liquid that has thedesired properties for a given application. These include, among others,imidazolium, pyrrolidinium and quaternary ammonium salts as cations andbis(trifluoromethanesulphonyl)imide, bis(fluorosulphonyl)imide, andhexafluorophosphate as anions. Based on their compositions, ionicliquids come in different classes that basically include aprotic, proticand zwitterionic types, each one suitable for a specific application.

Common cations of room temperature ionic liquids (RTILs) include, butnot limited to, tetraalkylammonium, di-, tri-, andtetra-alkylimidazolium, alkylpyridinium, dialkyl-pyrrolidinium,dialkylpiperidinium, tetraalkylphosphonium, and trialkylsulfonium.Common anions of RTILs include, but not limited to, BF₄ ⁻, B(CN)₄ ⁻,CH₃BF₃ ⁻, CH2CHBF₃ ⁻, CF₃BF₃ ⁻, C₂F₅BF₃ ⁻, n-C₃F₇BF₃ ⁻, n-C₄F₉BF₃ ⁻, PF₆⁻, CF₃CO₂ ⁻, CF₃SO₃ ⁻, N(SO₂CF₃)₂ ⁻, N(COCF₃)(SO₂CF₃)⁻, N(SO₂F)₂ ⁻,N(CN)₂ ⁻, C(CN)₃ ⁻, SeCN⁻, CuCl₂ ⁻, AlCl₄ ⁻, F(HF)_(2.3) ⁻, etc.Relatively speaking, the combination of imidazolium- or sulfonium-basedcations and complex halide anions such as AlCl₄ ⁻, BF₄ ⁻, CF₃CO₂ ⁻,CF₃SO₃ ⁻, NTf₂ ⁻, N(SO₂F)₂ ⁻, or F(HF)_(2.3) ⁻ results in RTILs withgood working conductivities.

RTILs can possess archetypical properties such as high intrinsic ionicconductivity, high thermal stability, low volatility, low (practicallyzero) vapor pressure, non-flammability, the ability to remain liquid ata wide range of temperatures above and below room temperature, highpolarity, high viscosity, and wide electrochemical windows. Theseproperties, except for the high viscosity, are desirable attributes whenit comes to using an RTIL as an electrolyte ingredient (a salt and/or asolvent) in a supercapacitor.

There is no restriction on the type of solid state electrolyte that canbe used for practicing the instant invention. The solid stateelectrolytes can be selected from a solid polymer-, metal oxide type(e.g. LIPON), solid sulfide type (e.g. Li₂S—P₂S₅), halide-type,hydride-type, and nitride-type, etc. The main inorganic solidelectrolytes that can be used are perovskite-type, NASICON-type,garnet-type and sulfide-type materials. The representative perovskitesolid electrolyte is Li_(3x)La_(2/3-x)TiO₃, which exhibits a lithium-ionconductivity exceeding 10⁻³ S/cm at room temperature.

NASICON-type compounds generally have an AM₂(PO₄)₃ formula with the Asite occupied by Li, Na or K. The M site is usually occupied by Ge, Zror Ti. In particular, the LiTi₂(PO₄)₃ system is particularly useful. Theionic conductivity of LiZr₂(PO₄)₃ is very low, but can be improved bythe substitution of Hf or Sn. This can be further enhanced withsubstitution to form Li_(1+x)M_(x)Ti_(2-x)(PO₄)₃ (M=Al, Cr, Ga, Fe, Sc,In, Lu, Y or La), with Al substitution being the most effective.

Garnet-type materials have the general formula A₃B₂Si₃O₁₂, in which theA and B cations have eight-fold and six-fold coordination, respectively.Some representative systems are Li₅La₃M₂O₁₂ (M=Nb or Ta), Li₆ALa₂M₂O₁₂(A=Ca, Sr or Ba; M=Nb or Ta), Li_(5.5)La₃M_(1.75)B_(0.25)O₁₂ (M=Nb orTa; B=In or Zr) and the cubic systems Li₇La₃Zr₂O₁₂ andLi_(7.06)M₃Y_(0.06)Zr_(1.94)O₁₂ (M=La, Nb or Ta). The room temperatureionic conductivity of Li_(6.5)La₃Zr_(1.75)Te_(0.25)O₁₂ is 1.02×10⁻³S/cm.

The polymer gel or polymer electrolyte may be based on ion-conductingpolymer having a lithium ion- or sodium ion conductivity from 10⁻⁷ to5×10⁻² S/cm. Examples include sodium ion-conducting or lithiumion-conducting polymer selected from the group consisting ofpoly(perfluoro sulfonic acid), sulfonated polytetrafluoroethylene,sulfonated perfluoroalkoxy derivatives of polytetra-fluoroethylene,sulfonated polysulfone, sulfonated poly(ether ketone), sulfonated poly(ether ether ketone), sulfonated polystyrene, sulfonated polyimide,sulfonated styrene-butadiene copolymers, sulfonated polychloro-trifluoroethylene, sulfonated perfluoroethylene-propylenecopolymer, sulfonated ethylene-chlorotrifluoroethylene copolymer,sulfonated polyvinylidenefluoride, sulfonated copolymers ofpolyvinylidenefluoride with hexafluoropropene and tetrafluoroethylene,sulfonated copolymers of ethylene and tetrafluoroethylene,polybenzimidazole, and chemical derivatives, copolymers, and blendsthereof.

In certain embodiments, the ion-conducting polymer may be preferablyselected from poly(ethylene oxide) (PEO), Polypropylene oxide,poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA),poly(vinylidene fluoride) (PVdF), Poly bis-methoxyethoxyethoxide-phosphazenex, Polyvinyl chloride, Polydimethylsiloxane,and poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), aderivative thereof, or a combination thereof.

Each of the presently invented anode particulates or cathodeparticulates contains particles of an active material (an anode activematerial or cathode active material), a conductive material, and anelectrolyte or portion of an electrolyte. These component materials maybe combined together to form secondary particles (particulates) havingsufficient integrity and rigidity to allow for subsequent handling (e.g.for dispensing into a cathode chamber or an anode chamber). A smallamount of polymer (particularly, an ion-conducting polymer), in anamount of 0.1%-35% (preferably 0.5-10%) of the total particulate weight,may be advantageously mixed into the particulates to help hold the threemajor ingredients together. Such an ion-conducting polymer preferably isthe same as or compatible with the polymer as part of a polymer gelelectrolyte or polymer solid electrolyte. This polymer may partiallyencapsulate the particulate.

There are two broad categories of particulate formation methods that canbe implemented to produce secondary particles (particulates): physicalmethods and chemical methods. The physical methods include pan-coating,air-suspension coating, ball-milling, centrifugal extrusion, vibrationnozzle, and spray-drying methods. The chemical methods includeinterfacial polycondensation, interfacial cross-linking, in-situpolymerization, and matrix polymerization. The polymer used must have anion conductivity no less than 10⁻⁷ S/cm.

Pan-coating method: The pan coating process involves tumbling the activematerial particles (along with conductive material particles andelectrolyte ingredients) in a pan or a similar device while theencapsulating material (e.g. monomer/oligomer, polymer melt,polymer/solvent solution) is applied slowly until a desired mixing anddegree of encapsulating is attained.

Air-suspension coating method: In the air suspension coating process,the solid particles (e.g. active material, conductive fibrils, lithiumsalt, etc.) are dispersed into the supporting air stream in anencapsulating chamber. A controlled stream of a polymer-solvent solution(polymer or its monomer or oligomer dissolved in a solvent; or itsmonomer or oligomer alone in a liquid state) is concurrently introducedinto this chamber, allowing the solution to hit and coat the suspendedparticles. These suspended particles are coated with a polymer or itsprecursor molecules while the volatile solvent is removed, leaving avery thin layer of polymer (or its precursor, which is cured/hardenedsubsequently) on surfaces of these particles. This process may berepeated several times until the required parameters, such asfull-coating thickness (i.e. encapsulating shell or wall thickness), areachieved. The air stream which supports the particles also helps to drythem, and the rate of drying is directly proportional to the temperatureof the air stream, which can be adjusted for optimized shell thickness.

In a preferred mode, the particles in the encapsulating zone portion maybe subjected to re-circulation for repeated coating. Preferably, theencapsulating chamber is arranged such that the particles pass upwardsthrough the encapsulating zone, then are dispersed into slower movingair and sink back to the base of the encapsulating chamber, enablingrepeated passes of the particles through the encapsulating zone untilthe desired encapsulating shell thickness is achieved.

Centrifugal extrusion: Mixtures of active material particles, conductiveadditive, and electrolyte may be well mixed and encapsulated with apolymer using a rotating extrusion head containing concentric nozzles.In this process, a stream of core fluid (slurry containing theseparticles dispersed in a solvent) is surrounded by a sheath of shellsolution or melt. As the device rotates and the stream moves through theair it breaks, due to Rayleigh instability, into droplets of core, eachcoated with the shell solution. While the droplets are in flight, themolten shell may be hardened or the solvent may be evaporated from theshell solution. If needed, the capsules can be hardened after formationby catching them in a hardening bath. Since the drops are formed by thebreakup of a liquid stream, the process is only suitable for liquid orslurry. A high production rate can be achieved. Up to 22.5 kg ofparticulates can be produced per nozzle per hour and extrusion headscontaining 16 nozzles are readily available.

Vibrational nozzle method: Core-shell encapsulation ormatrix-encapsulation of a mixture of active material-conductivematerial-electrolyte can be conducted using a laminar flow through anozzle and vibration of the nozzle or the liquid. The vibration has tobe done in resonance with the Rayleigh instability, leading to veryuniform droplets. The liquid can consist of any liquids with limitedviscosities (1-50,000 mPa·s): emulsions, suspensions or slurrycontaining the active material. The solidification can be done accordingto the used gelation system with an internal gelation (e.g. sol-gelprocessing, melt) or an external (additional binder system, e.g. in aslurry).

Spray-drying: Spray drying may be used to encapsulate particles of anactive material mixture when the active material mixture is dissolved orsuspended in a melt or polymer solution. In spray drying, the liquidfeed (solution or suspension) is atomized to form droplets which, uponcontacts with hot gas, allow solvent to get vaporized and thin polymershell to fully embrace the solid particles of the active material (plusconductive material and electrolyte ingredients).

Interfacial polycondensation and interfacial cross-linking: Interfacialpolycondensation entails introducing the two reactants to meet at theinterface where they react with each other. This is based on the conceptof the Schotten-Baumann reaction between an acid chloride and a compoundcontaining an active hydrogen atom (such as an amine or alcohol),polyester, polyurea, polyurethane, or urea-urethane condensation. Underproper conditions, thin flexible encapsulating shell (wall) formsrapidly at the interface. A solution of the active material mixture anda diacid chloride are emulsified in water and an aqueous solutioncontaining an amine and a polyfunctional isocyanate is added. A base maybe added to neutralize the acid formed during the reaction. Condensedpolymer shells form instantaneously at the interface of the emulsiondroplets. Interfacial cross-linking is derived from interfacialpolycondensation, wherein cross-linking occurs between growing polymerchains and a multi-functional chemical groups to form a polymer shellmaterial.

In-situ polymerization: In some micro-encapsulation processes, activematerials particles are fully coated with a monomer or oligomer first.Then, direct polymerization and cross-linking of the monomer or oligomeris carried out on the surfaces of these material particles.

Matrix polymerization: This method involves dispersing and embedding acore material (the mixture of active material particles, conductivematerial, and electrolyte ingredients) in a polymeric matrix duringformation of the particles. This can be accomplished via spray-drying,in which the particles are formed by evaporation of the solvent from thematrix material. Another possible route is the notion that thesolidification of the matrix is caused by a chemical change.

In what follows, we provide examples for a large number of differenttypes of anode active materials, cathode active materials, andconductive materials to illustrate the best mode of practicing theinstant invention. Theses illustrative examples and other portions ofinstant specification and drawings, separately or in combinations, aremore than adequate to enable a person of ordinary skill in the art topractice the instant invention. However, these examples should not beconstrued as limiting the scope of instant invention.

Example 1: Anode Particulates of Si Nanoparticles, Carbon Nanofibers(CNFs), and Lithium Salt

First, Si nanoparticles and CNFs at a weight ratio of 95:5 weredispersed in an organic liquid electrolyte, containing 1.0 M of LiPF₆dissolved in PC-EC, to form a slurry. Then, 0.2% by wt. of poly(ethyleneoxide) (PEO) was added into the slurry to form a gel-like mass, whichwas diluted by adding some acetonitrile (AN) to the extent that theoverall solid content was approximately 10% by weight. The resultingslurry was spray-dried to remove AN and form anode particulates thatwere approximately 15-32 μm in diameter.

Example 2: Anode Particulates of Cobalt Oxide (Co₃O₄)—CNT-Lithium Salt

An appropriate amount of inorganic salts Co(NO₃)₂.6H₂O and ammoniasolution (NH₃.H₂O, 25 wt. %) were mixed together. The resultingsuspension was stirred for several hours under an argon flow to ensure acomplete reaction. The obtained Co(OH)₂ precursor suspension wascalcined at 450° C. in air for 2 h to form particles of the layeredCo₃O₄. Portion of the Co₃O₄ particles was then mixed and coated withultrahigh molecular weight (UHMW) PEO according to the followingprocedure:

UHMW PEO having a MW of 5.0×10⁶ was dissolved in DI-water (1.6 wt. %) toform a homogenous and clear solution. Then, two routes were followed toprepare polymer-containing Co₃O₄ particles. In the first route, Co₃O₄particles and CNTs, at a weight ratio from 96:4 to 70:30, were dispersedin the UHMW PEO-water solution to form a series of slurries. The slurrywas each spray-dried to form particulates of polymer-encapsulated Co₃O₄particles.

In the second route, 5-35% of lithium salt (LiClO₄) was dissolved in thePEO-water solution to form a series of lithium-salt containingsolutions. Then, Co₃O₄ particles and CNTs, at a weight ratio from 96:4to 70:30, were dispersed in the lithium salt-containing UHMW PEO-watersolution to form a series of slurries. Each slurry was spray-dried toform particulates of polymer/lithium salt/Co₃O₄ particles, wherein theCNTs were found to exceed percolation as reflected by a good electricalconductivity value, typically from wherein said anode particulate has anelectrical conductivity from about 10⁻¹ S/cm to about 20 S/cm.

In the preparation of the desired lithium battery cells, a solvent(ethylene carbonate or EC+a lithium salt) was added into the cell,allowing the solvent to permeate into the amorphous zones of the polymerphase to form a polymer gel electrolyte in the anode particulates.

Example 3: Particulates of Tin Oxide-Lithium Borofluoride(LiBF₄)—PC/DEC-Expanded Graphite Platelets

Tin oxide (SnO₂) nanoparticles were obtained by the controlledhydrolysis of SnCl₄.5H₂O with NaOH using the following procedure:SnCl₄.5H₂O (0.95 g, 2.7 m-mol) and NaOH (0.212 g, 5.3 m-mol) weredissolved in 50 mL of distilled water each. The NaOH solution was addeddrop-wise under vigorous stirring to the tin chloride solution at a rateof 1 mL/min. This solution was homogenized by sonication for 5 m in.Subsequently, the resulting hydrosol was reacted with H₂SO₄. To thismixed solution, few drops of 0.1 M of H₂SO₄ were added to flocculate theproduct. The precipitated solid was collected by centrifugation, washedwith water and ethanol, and dried in vacuum. The dried product, SnO₂nanoparticles, was heat-treated at 400° C. for 2 h under Ar atmosphere.

Ultra-high molecular weight polyacrylonitrile (UHMW PAN) was used hereto hold ingredients of an anode particulate together. UHMW PAN (0.1 g)was dissolved in 5 ml of dimethylformamide (DMF) to form a solution. TheSnO₂ nanoparticles, lithium borofluoride (LiBF₄), and fine platelets ofexpanded graphite (0.3 μm wide and 110 nm thick) were then dispersed inthe solution to form a slurry. The slurry was then subjected to amicro-encapsulation procedure using a vibration nozzle method to producesolid anode particulates.

Example 4: Preparation of Graphene Oxide (GO) and Reduced Graphene Oxide(RGO) Nanosheets (as a Preferred Conductive Material) from NaturalGraphite Powder

Natural graphite was used as the starting material. GO was obtained byfollowing the well-known modified Hummers method, which involved twooxidation stages. In a typical procedure, the first oxidation wasachieved in the following conditions: 1100 mg of graphite was placed ina 1000 mL boiling flask. Then, 20 g of K₂S₂O₈, 20 g of P₂O₅, and 400 mLof a concentrated aqueous solution of H₂SO₄ (96%) were added in theflask. The mixture was heated under reflux for 6 hours and then letwithout disturbing for 20 hours at room temperature. Oxidized graphitewas filtered and rinsed with abundant distilled water until neutral pH.A wet cake-like material was recovered at the end of this firstoxidation.

For the second oxidation process, the previously collected wet cake wasplaced in a boiling flask that contains 69 mL of a concentrated aqueoussolution of H₂SO₄ (96%). The flask was kept in an ice bath as 9 g ofKMnO₄ was slowly added. Care was taken to avoid overheating. Theresulting mixture was stirred at 35° C. for 2 hours (the sample colorturning dark green), followed by the addition of 140 mL of water. After15 min, the reaction was halted by adding 420 mL of water and 15 mL ofan aqueous solution of 30 wt % H₂O₂. The color of the sample at thisstage turned bright yellow. To remove the metallic ions, the mixture wasfiltered and rinsed with a 1:10 HCl aqueous solution. The collectedmaterial was gently centrifuged at 2700 g and rinsed with deionizedwater. The final product was a wet cake that contained 1.4 wt % of GO,as estimated from dry extracts. Subsequently, liquid dispersions of GOplatelets were obtained by lightly sonicating wet-cake materials, whichwere diluted in deionized water.

Surfactant-stabilized RGO (RGO-BS) was obtained by diluting the wet-cakein an aqueous solution of surfactants instead of pure water. Acommercially available mixture of cholate sodium (50 wt. %) anddeoxycholate sodium (50 wt. %) salts provided by Sigma Aldrich was used.The surfactant weight fraction was 0.5 wt. %. This fraction was keptconstant for all samples. Sonication was performed using a BransonSonifier S-250A equipped with a 13 mm step disruptor horn and a 3 mmtapered micro-tip, operating at a 20 kHz frequency. For instance, 10 mLof aqueous solutions containing 0.1 wt. % of GO was sonicated for 10 minand subsequently centrifuged at 2700 g for 30 min to remove anynon-dissolved large particles, aggregates, and impurities. Chemicalreduction of as-obtained GO to yield RGO was conducted by following themethod, which involved placing 10 mL of a 0.1 wt. % GO aqueous solutionin a boiling flask of 50 mL. Then, 10 μL of a 35 wt. % aqueous solutionof N₂H₄ (hydrazine) and 70 mL of a 28 wt. % of an aqueous solution ofNH₄OH (ammonia) were added to the mixture, which was stabilized bysurfactants. The solution was heated to 90° C. and refluxed for 1 h. ThepH value measured after the reaction was approximately 9. The color ofthe sample turned dark black during the reduction reaction.

RGO sheets were used as a conductive material that could form a 3Dnetwork of electron-conducting pathways in an anode particulate or acathode particulate. In addition, prelithiated RGO (e.g. RGO+lithiumparticles or RGO pre-deposited with lithium coating) was also used as ananode active material.

Example 5: Preparation of Pristine Graphene Sheets (0% Oxygen)

Recognizing the possibility of the high defect population in GO sheetsacting to reduce the conductivity of individual graphene plane, wedecided to study if the use of pristine graphene sheets (non-oxidizedand oxygen-free, non-halogenated and halogen-free, etc.) can lead to aconductive additive (or a discrete conductive material layer) having ahigh electrical and thermal conductivity. Prelithiated pristine grapheneand pre-sodiated pristine graphene were also used as an anode activematerial for a lithium-ion battery and a sodium-ion battery,respectively. Pristine graphene sheets were produced by using the directultrasonication or liquid-phase production process.

In a typical procedure, five grams of graphite flakes, ground toapproximately 20 μm or less in sizes, were dispersed in 1,000 mL ofdeionized water (containing 0.1% by weight of a dispersing agent, Zonyl®FSO from DuPont) to obtain a suspension. An ultrasonic energy level of85 W (Branson 5450 Ultrasonicator) was used for exfoliation, separation,and size reduction of graphene sheets for a period of 15 minutes to 2hours. The resulting graphene sheets are pristine graphene that havenever been oxidized and are oxygen-free and relatively defect-free.Pristine graphene is essentially free from any non-carbon elements.

Pristine graphene sheets were used as a conductive material in an anodeparticulate or a cathode particulate.

Example 6: Preparation of Prelithiated and Pre-Sodiated GrapheneFluoride Sheets as an Anode Active Material of a Lithium-Ion Battery orSodium-Ion Battery

Several processes have been used by us to produce GF, but only oneprocess is herein described as an example. In a typical procedure,highly exfoliated graphite (HEG) was prepared from intercalated compoundC₂F.xClF₃. HEG was further fluorinated by vapors of chlorine trifluorideto yield fluorinated highly exfoliated graphite (FHEG). Pre-cooledTeflon reactor was filled with 20-30 mL of liquid pre-cooled ClF₃, thereactor was closed and cooled to liquid nitrogen temperature. Then, nomore than 1 g of HEG was put in a container with holes for ClF₃ gas toaccess and situated inside the reactor. In 7-10 days a gray-beigeproduct with approximate formula C₂F was formed.

Subsequently, a small amount of FHEG (approximately 0.5 mg) was mixedwith 20-30 mL of an organic solvent (methanol and ethanol, separately)and subjected to an ultrasound treatment (280 W) for 30 min, leading tothe formation of homogeneous yellowish dispersions. Upon removal ofsolvent, the dispersion became a brownish powder. The graphene fluoridepowder was mixed with surface-stabilized lithium powder and in a liquidelectrolyte, allowing for prelithiation to occur before being includedin an anode particulate. Pre-sodiation of graphene fluoride wasconducted electrochemically using a procedure substantially similar to aplating procedure.

Example 7: Lithium Iron Phosphate (LFP) Cathode of a Lithium MetalBattery

LFP powder, un-coated or carbon-coated, is commercially available fromseveral sources. A gel electrolyte (PEO-EC/DEC) containing a lithiumsalt was first prepared. LFP particles and GO sheets (prepared inExample 4) were then dispersed into the gel electrolyte. The resultingslurry was then simply heated in an oven to form cathode particulateshaving a diameter from 25-36 μm.

Example 8: Preparation of Disodium Terephthalate (Na₂C₈H₄O₄) as an AnodeActive Material of a Sodium-Ion Battery

Pure disodium terephthalate was obtained by the recrystallizationmethod. An aqueous solution was prepared via the addition ofterephthalic acid to an aqueous NaOH solution and then ethanol (EtOH)was added to the mixture to precipitate disodium terephthalate in awater/EtOH mixture. Because of resonance stabilization, terephtalic acidhas relatively low pKa values, which allow easy deprotonation by NaOH,affording disodium terephthalate (Na₂TP) through the acid-basechemistry. In a typical procedure, terephthalic acid (3.00 g, 18.06mmol) was treated with sodium hydroxide (1.517 g, 37.93 mmol) in EtOH(60 mL) at room temperature. After 24 h, the suspended reaction mixturewas centrifuged and the supernatant solution was decanted. Theprecipitate was re-dispersed in EtOH and then centrifuged again. Thisprocedure was repeated twice to yield a white solid. The product wasdried in vacuum at 150° C. for 1 h. In a separate sample, GO was addedto aqueous NaOH solution (5% by wt. of GO sheets) to prepare sheets ofgraphene-supported disodium terephthalate under comparable reactionconditions.

The carbon-disodium terephthalate mixture powder and graphene sheets (orgraphene-supported disodium terephthalate) were added into a sodiumsalt-electrolyte solution (sodium perchlorate (NaClO₄+EC and MEC) toprepare a suspension. The suspension was then made into cathodeparticulates using a vibration nozzle method.

Example 9: V₂O₅ as an Example of a Transition Metal Oxide Cathode ActiveMaterial of a Lithium Battery

V₂O₅ powder alone is commercially available. For the preparation of agraphene-supported V₂O₅ powder sample, in a typical experiment, vanadiumpentoxide gels were obtained by mixing V₂O₅ in a LiCl aqueous solution.The Lit exchanged gels obtained by interaction with LiCl solution (theLi:V molar ratio was maintained as 1:1) was mixed with a GO suspensionand then placed in a Teflon-lined stainless steel 35 ml autoclave,sealed, and heated up to 180° C. for 12 h. After such a hydrothermaltreatment, the green solids were collected, thoroughly washed,ultrasonicated for 2 minutes, and dried at 70° C. for 12 h followed bymixing with another 0.1% GO in water, ultrasonicating to break downnanobelt sizes, and then spray-drying at 200° C. to obtaingraphene-embraced composite particulates.

Both V₂O₅ powder (with a mixture of carbon black powder and graphenesheets as a conductive additive) and graphene-supported V₂O₅ powder,separately, along with a liquid electrolyte, were then made into cathodeparticulates.

Example 10: LiCoO₂ as an Example of Lithium Transition Metal OxideCathode Active Material for a Lithium-Ion Battery

Commercially available LiCoO₂ powder, carbon black powder (or RGOsheets) and were dispersed in PC-EC/LiPF₆ electrolyte (containing 0.2%of polyethylene glycol) to form a slurry. The slurry was spray-dried toform cathode particulates. Some of the LiCoO₂ powder, not in aparticulate form of the present invention, was used to prepareconventional cathode to pair up with the presently invented anodeparticulate-based anode (prepared in Example 1) and, separately, aconventional anode.

Example 11: Cathode Active Materials Based on Mixed Transition MetalOxides for a Sodium-Ion Cell

As examples, for the synthesis of Na_(1.0)Li_(0.2)Ni_(0.25)Mn_(0.75)O₆,Ni_(0.25)Mn_(0.75)CO₃, or Ni_(0.25)Mn_(0.75)(OH)₂ cathode activematerial, Na₂CO₃, and Li₂CO₃ were used as starting compounds. Materialsin appropriate mole ratios were ground together and heat-treated; firstat 500° C. for 8 h in air, then finally at 800° C. for 8 h in air, andfurnace cooled. For electrode preparation using a conventionalprocedure, a sheet of aluminum foil was coated withN-methylpyrrolidinone (NMP) slurry of the cathode mixture. The electrodemixture is composed of 82 wt % active oxide material, 8 wt % conductivecarbon black (Timcal Super-P), and 10 wt. % PVDF binder (Kynar). BothNa_(1.0)Li_(0.2)Ni_(0.25)Mn_(0.75)O_(δ) powder (with a carbon blackpowder as a conductive additive) and graphene-supportedNa_(1.0)Li_(0.2)Ni_(0.25)Mn_(0.75)O_(δ) powder, separately, were used.After casting, the electrode was initially dried at 70° C. for 2 h,followed by dynamic vacuum drying at 80° C. for at least 6 h.

For the preparation of the instant battery, no NMP was involved.Particles of Ni_(0.25)Mn_(0.75)CO₃ and CNTs were dispersed in anelectrolyte of 1 M of NaClO₄) in PC/EC to form a slurry. The slurry wasspray-dried to form cathode particulates, which were made into acathode. Na powder, mixed with graphene sheets, was used as the anode. Aconventional battery cell was also made for comparison purpose. Thecells were galvanostatically cycled to a cutoff of 4.2 V vs. Na/Na⁺ (15mA/g) and then discharged at various current rates to a cutoff voltageof 2.0 V.

In all battery cells prepared, charge storage capacities were measuredperiodically and recorded as a function of the number of cycles. Thespecific discharge capacity herein referred to is the total chargeinserted into the cathode during the discharge, per unit mass of thecomposite cathode (counting the weights of cathode active material,conductive additive or support, binder, and any optional additivecombined, but excluding the current collector). The specific chargecapacity refers to the amount of charges per unit mass of the compositecathode. The specific energy and specific power values presented in thissection are based on the total cell weight for all pouch cells. Themorphological or micro-structural changes of selected samples after adesired number of repeated charging and recharging cycles were observedusing both transmission electron microscopy (TEM) and scanning electronmicroscopy (SEM).

Example 12: Na₃V₂(PO₄)₃/C and Na₃V₂(PO₄)₃/Graphene Cathodes

The Na₃V₂(PO₄)₃/C sample was synthesized by a solid state reactionaccording to the following procedure: a stoichiometric mixture ofNaH₂PO₄.2H₂O (99.9%, Alpha) and V₂O₃ (99.9%, Alpha) powders was put inan agate jar as a precursor and then the precursor was ball-milled in aplanetary ball mill at 400 rpm in a stainless steel vessel for 8 h.During ball milling, for the carbon coated sample, sugar (99.9%, Alpha)was also added as the carbon precursor and the reductive agent, whichprevents the oxidation of V³⁺. After ball milling, the mixture waspressed into a pellet and then heated at 900° C. for 24 h in Aratmosphere. Separately, the Na₃V₂(PO₄)₃/graphene cathode was prepared ina similar manner, but with sugar replaced by graphene oxide. Cathodeparticulates composed of these particles, a polymer gel electrolyte (1 Mof NaPF₆ salt in PC+DOL, plus 0.1% PEO) were produced using apan-coating method. The cathode active materials were used in several Nametal cells containing 1 M of NaPF₆ salt in PC+DOL as the electrolyte.Both conventional Na metal cells and instant cells featuring cathodeparticulates were made.

Example 13: Organic Material (Li₂C₆O₆) as a Cathode Active Material of aLithium Metal Battery

In order to synthesize dilithium rhodizonate (Li₂C₆O₆), the rhodizonicacid dihydrate (species 1 in the following scheme) was used as aprecursor. A basic lithium salt, Li₂CO₃ can be used in aqueous media toneutralize both enediolic acid functions. Strictly stoichiometricquantities of both reactants, rhodizonic acid and lithium carbonate,were allowed to react for 10 hours to achieve a yield of 90%. Dilithiumrhodizonate (species 2) was readily soluble even in a small amount ofwater, implying that water molecules are present in species 2. Water wasremoved in a vacuum at 180° C. for 3 hours to obtain the anhydrousversion (species 3).

A mixture of a cathode active material (Li₂C₆O₆) and a conductiveadditive (carbon black, 15%) was ball-milled for 10 minutes and theresulting blend was grinded to produce composite particles. Theelectrolyte was 1M of lithium hexafluorophosphate (LiPF₆) in PC-EC.

It may be noted that the two Li atoms in the formula Li₂C₆O₆ are part ofthe fixed structure and they do not participate in reversible lithiumion storing and releasing. This implies that lithium ions must come fromthe anode side. Hence, there must be a lithium source (e.g. lithiummetal or lithium metal alloy) at the anode. The anode current collector(Cu foil) is deposited with a layer of lithium (e.g. via sputtering orelectrochemical plating). This can be done prior to assembling thelithium-coated layer (or simply a lithium foil), a porous separator, andan impregnated cathode roll into a casing envelop. The cathode activematerial and conductive additive (Li₂C₆O₆/C composite particles+CNTs)wetted with the liquid electrolyte were made into cathode particulatesusing a pan-coating method. For comparison, a corresponding conventionalLi metal cell was also fabricated by the conventional procedures ofslurry coating, drying, laminating, packaging, and electrolyteinjection.

Example 14: Organic Material (Na₂C₆O₆) as a Cathode Active Material of aSodium Metal Battery

In order to synthesize disodium rhodizonate (Na₂C₆O₆), the rhodizonicacid dihydrate (species 1 in the following scheme) was used as aprecursor. A basic sodium salt, Na₂CO₃ can be used in aqueous media toneutralize both enediolic acid functions. Strictly stoichiometricquantities of both reactants, rhodizonic acid and sodium carbonate, wereallowed to react for 10 hours to achieve a yield of 80%. Disodiumrhodizonate (species 2) was readily soluble even in a small amount ofwater, implying that water molecules are present in species 2. Water wasremoved in a vacuum at 180° C. for 3 hours to obtain the anhydrousversion (species 3).

A mixture of a cathode active material (Na₂C₆O₆) and a conductiveadditive (carbon black, 15%) was ball-milled for 10 minutes and theresulting blend was grinded to produce composite particles. Theelectrolyte was 1M of sodium hexafluorophosphate (NaPF₆) in PC-EC.

The two Na atoms in the formula Na₂C₆O₆ are part of the fixed structureand they do not participate in reversible lithium ion storing andreleasing. The sodium ions must come from the anode side. Hence, theremust be a sodium source (e.g. sodium metal or sodium metal alloy) at theanode. An anode current collector (Cu foil) was deposited with a layerof sodium (e.g. via sputtering or electrochemical plating). This wasdone prior to assembling the sodium-coated layer or simply a sodiumfoil, a porous separator, and a cathode roll into a dry cell. Thecathode active material and conductive additive (Na₂C₆O₆/C compositeparticles+RGO) dispersed in the liquid electrolyte were made intocathode particulates.

Example 15: Metal Naphthalocyanine-RGO Hybrid Cathode of a Lithium MetalBattery

CuPc-coated graphene sheets were obtained by vaporizing CuPc in achamber along with a graphene film (5 nm) prepared from spin coating ofRGO-water suspension. The resulting coated film was cut and milled toproduce CuPc-coated graphene sheets, which were mixed with a gelelectrolyte (3.5 M of LiClO₄ in propylene carbonate) and made intocathode particulates. This battery has a lithium metal foil as the anodeactive material and 3.5 M of LiClO₄ in propylene carbonate (PC) solutionas the electrolyte. A conventional lithium metal cell was made andtested for comparison.

Example 16: Preparation of MoS₂/RGO Hybrid Material as a Cathode ActiveMaterial of a Lithium Metal Battery

A wide variety of inorganic materials were investigated in this example.For instance, an ultra-thin MoS₂/RGO hybrid was synthesized by aone-step solvothermal reaction of (NH₄)₂MoS₄ and hydrazine in anN,N-dimethylformamide (DMF) solution of oxidized graphene oxide (GO) at200° C. In a typical procedure, 22 mg of (NH₄)₂MoS₄ was added to 10 mgof GO dispersed in 10 ml of DMF. The mixture was sonicated at roomtemperature for approximately 10 min until a clear and homogeneoussolution was obtained. After that, 0.1 ml of N₂H₄—H₂O was added. Thereaction solution was further sonicated for 30 min before beingtransferred to a 40 mL Teflon-lined autoclave. The system was heated inan oven at 200° C. for 10 h. Product was collected by centrifugation at8000 rpm for 5 min, washed with DI water and recollected bycentrifugation. The washing step was repeated for at least 5 times toensure that most DMF was removed. Finally, product was dried, mixed withliquid electrolyte and some CNFs to produce cathode particulates.

Example 17: Preparation of Two-Dimensional (2D) Layered Bi₂Se₃Chalcogenide Nanoribbons

The preparation of (2D) layered Bi₂Se₃ chalcogenide nanoribbons iswell-known in the art. For instance, Bi₂Se₃ nanoribbons were grown usingthe vapor-liquid-solid (VLS) method. Nanoribbons herein produced are, onaverage, 30-55 nm thick with widths and lengths ranging from hundreds ofnanometers to several micrometers. Larger nanoribbons were subjected toball-milling for reducing the lateral dimensions (length and width) tobelow 200 nm. Nanoribbons prepared by these procedures (with or withoutthe presence of graphene sheets or exfoliated graphite flakes) weremixed with some CNTs and dispersed in a desired polymer gel electrolyte(LiPF₆+PC-EC+PEO) to form a slurry. The slurry was made into cathodeparticulates using spray-drying.

Example 18: Preparation of Graphene-Supported MnO₂ Cathode ActiveMaterial

The MnO₂ powder was synthesized by two methods (each with or without thepresence of graphene sheets). In one method, a 0.1 mol/L KMnO₄ aqueoussolution was prepared by dissolving potassium permanganate in deionizedwater. Meanwhile 13.32 g surfactant of high purity sodiumbis(2-ethylhexyl) sulfosuccinate was added in 300 mL iso-octane (oil)and stirred well to get an optically transparent solution. Then, 32.4 mLof 0.1 mol/L KMnO₄ solution and selected amounts of GO solution wereadded in the solution, which was ultrasonicated for 30 min to prepare adark brown precipitate. The product was separated, washed several timeswith distilled water and ethanol, and dried at 80° C. for 12 h. Thesample is graphene-supported MnO₂ in a powder form, which was mixed in aliquid electrolyte to form cathode particulates.

Example 19: Preparation and Electrochemical Testing of Various AlkaliMetal Battery Cells

For most of the anode and cathode active materials investigated, weprepared alkali metal-ion cells or alkali metal cells using both thepresently invented method and the conventional method.

With the conventional method, a typical anode composition includes 85wt. % active material (e.g., Si- or Co₃O₄-coated graphene sheets), 7 wt.% acetylene black (Super-P), and 8 wt. % polyvinylidene fluoride binder(PVDF, 5 wt. % solid content) dissolved in N-methyl-2-pyrrolidinoe(NMP). After coating the slurries on Cu foil, the electrodes were driedat 120° C. in vacuum for 2 h to remove the solvent. An anode layer,separator layer (e.g. Celgard 2400 membrane), and a cathode layer arethen laminated together and housed in a plastic-Al envelop. The cell isthen injected with 1 M LiPF₆ electrolyte solution dissolved in a mixtureof ethylene carbonate (EC) and diethyl carbonate (DEC) (EC-DEC, 1:1v/v). In some cells, ionic liquids were used as the liquid electrolyte.The cell assemblies were made in an argon-filled glove-box.

With the instant cell, typically no binder resin is needed or used,saving 8% weight (reduced amount of non-active materials). The cell wasmade into a shape as illustrated in FIG. 1(E). The cathode is typicallycomposed of a mass of cathode particulates disposed in a container. AnAl foil is disposed at the bottom of the container as a cathode currentcollector. A certain amount of anode particulates, with or without anadditional amount of a liquid electrolyte, were then extruded into anoderods having a diameter from 50 μm to 1 cm and having a thin Cu wire asan anode current collector. These rods were wrapped around with a porousmembrane (Celgard 2400) and then inserted into the cathode bath. One ormultiple anode rods can be inserted into a cathode bath.

In certain cases, as an alternative battery cell configuration, a massof anode particulates was disposed in a container and one or multiplecathode rods wrapped with a porous membrane are inserted into the anodemass.

The cyclic voltammetry (CV) measurements were carried out using an Arbinelectrochemical workstation at a typical scanning rate of 1 mV/s. Inaddition, the electrochemical performances of various cells were alsoevaluated by galvanostatic charge/discharge cycling at a current densityof from 50 mA/g to 10 A/g. For long-term cycling tests, multi-channelbattery testers manufactured by LAND were used.

In lithium-ion battery industry, it is a common practice to define thecycle life of a battery as the number of charge-discharge cycles thatthe battery suffers 20% decay in capacity based on the initial capacitymeasured after the required electrochemical formation.

Example 20: Representative Testing Results for Lithium Cells

For each sample, several current densities (representingcharge/discharge rates) were imposed to determine the electrochemicalresponses, allowing for calculations of energy density and power densityvalues required of the construction of a Ragone plot (power density vs.energy density).

Shown in FIG. 3 are Ragone plots (gravimetric and volumetric powerdensity vs. energy density) of lithium-ion battery cells containinggraphite particles as the anode active material and carbon-coated LFPparticles as the cathode active materials. Two of the four data curvesare for the presently invented cells (featuring the invented anodeparticulates and cathode particulates) prepared according to anembodiment of instant invention and the other two by the conventionalslurry coating of electrodes (roll-coating). Several significantobservations can be made from these data:

Both the gravimetric and volumetric energy densities and power densitiesof the lithium-ion battery cells prepared by the presently inventedmethod are significantly higher than those of their counterpartsprepared via the conventional roll-coating method (denoted as“conventional”). The gravimetric energy density is increased from 165Wh/kg of a conventional cell to 205 Wh/kg of a currently invented cell.Also surprisingly, the volumetric energy density is increased from 412.5Wh/L to 573 Wh/L. This latter value of 573 Wh/L has never beenpreviously achieved with a conventional lithium-ion battery using agraphite anode and a lithium iron phosphate cathode.

These differences are likely due to the significantly higher activematerial mass loading associated with the presently invented cells,reduced proportion of overhead (non-active) components relative to theactive material weight/volume, and surprisingly better utilization ofthe electrode active material (most, if not all, of the graphiteparticles and LFP particles contributing to the lithium ion storagecapacity; no dry pockets or ineffective spots in the electrode,particularly under high charge/discharge rate conditions). These havenot been taught, suggested, or even slightly hinted in the art oflithium-ion battery. Furthermore, the maximum power density is increasedfrom 621 W/kg to 1,440 W/kg. This might have been due to significantlyreduced internal resistance against electron transport and lithium iontransport.

FIG. 4 shows the Ragone plots (both gravimetric and volumetric powerdensity vs. gravimetric and volumetric energy density) of two cells,both containing graphene-embraced Si nanoparticles as the anode activematerial and LiCoO₂ nanoparticles as the cathode active material. Theexperimental data were obtained from the invented Li-ion battery cellsthat presently invented anode particulate and cathode particulates andthe conventional cells prepared by the conventional slurry coating ofelectrodes.

These data indicate that both the gravimetric and volumetric energydensities and power densities of the battery cells prepared by thepresently invented method are significantly higher than those of theircounterparts prepared via the conventional method. Again, thedifferences are huge. The conventionally made cells exhibit agravimetric energy density of 265 Wh/kg and volumetric energy density of689 Wh/L, but the presently invented cells deliver 403 Wh/kg and 1,188Wh/L, respectively. The cell-level energy density of 1,188 Wh/L, hasnever been previously achieved with any conventional rechargeablelithium battery. The power densities as high as 1,978 W/kg and 5,750 W/Lare also unprecedented for lithium-ion batteries. The power densities ofthe cells prepared according to the presently invented approach arealways significantly higher than those of the corresponding cellsprepared by conventional processes.

These energy density and power density differences are mainly due to thehigh active material mass loading (>25 mg/cm² in the anode and >45mg/cm² in the cathode) associated with the presently invented cells,reduced proportion of overhead (non-active) components relative to theactive material weight/volume, and the ability of the inventive methodto better utilize the active material particles (all particles beingaccessible to liquid electrolyte and fast ion and electron kinetics).

Shown in FIG. 5 are Ragone plots of lithium metal batteries containing alithium foil as the anode active material, dilithium rhodizonate(Li₂C₆O₆) as the cathode active material, and lithium salt(LiPF₆)—PC/DEC as organic liquid electrolyte. The data are for bothlithium metal cells prepared by the presently invented method and thoseby the conventional slurry coating of electrodes. These data indicatethat both the gravimetric and volumetric energy densities and powerdensities of the lithium metal cells prepared by the presently inventedmethod are significantly higher than those of their counterpartsprepared via the conventional method. Again, the differences are hugeand are likely due to the significantly higher active material massloading (not just mass loading) associated with the presently inventedcells, reduced proportion of overhead (non-active) components relativeto the active material weight/volume, and surprisingly betterutilization of the electrode active material (most, if not all, of theactive material contributing to the lithium ion storage capacity; no drypockets or ineffective spots in the electrode, particularly under highcharge/discharge rate conditions).

Quite noteworthy and unexpected is the observation that the gravimetricenergy density of the presently invented lithium metal-organic cathodecell is as high as 422 Wh/kg, higher than those of all rechargeablelithium-metal or lithium-ion batteries ever reported (recall thatcurrent Li-ion batteries store 150-220 Wh/kg based on the total cellweight). Also, quite astonishing is the observation that the volumetricenergy density of such an organic cathode-based battery is as high as844 Wh/L, an unprecedentedly high value that tops those of allconventional lithium-ion and lithium metal batteries ever reported.Furthermore, for organic cathode active material-based lithiumbatteries, a gravimetric power density of 1,766 W/kg and maximumvolumetric power density of 5,125 W/L would have been un-thinkable.

It is of significance to point out that reporting the energy and powerdensities per weight of active material alone on a Ragone plot, as didby many researchers, may not give a realistic picture of the performanceof the assembled supercapacitor cell. The weights of other devicecomponents also must be taken into account. These overhead components,including current collectors, electrolyte, separator, binder,connectors, and packaging, are non-active materials and do notcontribute to the charge storage amounts. They only add weights andvolumes to the device. Hence, it is desirable to reduce the relativeproportion of overhead component weights and increase the activematerial proportion. However, it has not been possible to achieve thisobjective using conventional battery production processes. The presentinvention overcomes this long-standing, most serious problem in the artof lithium batteries.

In commercial lithium-ion batteries having an electrode thickness of100-200 μm, the weight proportion of the anode active material (e.g.graphite or carbon) in a lithium-ion battery is typically from 12% to17%, and that of the cathode active material (for inorganic material,such as LiMn₂O₄) from 22% to 41%, or from 10% to 15% for organic orpolymeric. Hence, a factor of 3 to 4 is frequently used to extrapolatethe energy or power densities of the device (cell) from the propertiesbased on the active material weight alone. In most of the scientificpapers, the properties reported are typically based on the activematerial weight alone and the electrodes are typically very thin (<<100μm, and mostly <<50 μm). The active material weight is typically from 5%to 10% of the total device weight, which implies that the actual cell(device) energy or power densities may be obtained by dividing thecorresponding active material weight-based values by a factor of 10 to20. After this factor is taken into account, the properties reported inthese papers do not really look any better than those of commercialbatteries. Thus, one must be very careful when it comes to read andinterpret the performance data of batteries reported in the scientificpapers and patent applications.

Because the weight of the anode and cathode active materials combinedaccounts for up to about 30%-50% of the total mass of the packagedcommercial lithium batteries, a factor of 30%-50% must be used toextrapolate the energy or power densities of the device from theperformance data of the active materials alone. Thus, the energy densityof 500 Wh/kg of combined graphite and NMC (lithium nickel manganesecobalt oxide) weights will translate to about 150-250 Wh/kg of thepackaged cell. However, this extrapolation is only valid for electrodeswith thicknesses and densities similar to those of commercial electrodes(150 μm or about 15 mg/cm² of the graphite anode and 30 mg/cm² of NMCcathode). An electrode of the same active material that is thinner orlighter will mean an even lower energy or power density based on thecell weight. Thus, it would be desirable to produce a lithium-ionbattery cell having a high active material proportion. Unfortunately, ithas not been previously possible to achieve a total active materialproportion greater than 45% by weight in most of the commerciallithium-ion batteries.

The presently invented method enables the lithium batteries to go wellbeyond these limits for all active materials investigated. As a matterof fact, the instant invention makes it possible to elevate the activematerial proportion above 90% if so desired; but typically from 45% to85%, more typically from 40% to 80%, even more typically from 40% to75%, and most typically from 50% to 70%.

Example 21: Representative Testing Results of Sodium Metal Cells

Shown in FIG. 6 are Ragone plots (gravimetric and volumetric powerdensity vs. energy density) of Na-ion battery cells containing hardcarbon particles as the anode active material and carbon-coatedNa₃V₂(PO₄)₂F₃ particles as the cathode active materials. Two of the fourdata curves are for the cells (containing anode particulates and cathodeparticulates) prepared according to an embodiment of instant inventionand the other two by the conventional slurry coating of electrodes(roll-coating). Several significant observations can be made from thesedata:

Both the gravimetric and volumetric energy densities and power densitiesof the sodium-ion battery cells prepared by the presently inventedmethod are significantly higher than those of their counterpartsprepared via the conventional roll-coating method (denoted as“conventional”). The gravimetric energy density for the conventionalNa-ion cell is 115 Wh/kg, but that for the particulate-based Na-ion cellis 158 Wh/kg. Also surprisingly, the volumetric energy density isincreased from 241 Wh/L to 498 Wh/L by using the presently inventedapproach. This latter value of 496 Wh/L is exceptional for aconventional sodium-ion battery using a hard carbon anode and a sodiumtransition metal phosphate-type cathode.

These huge differences are likely due to the significantly higher activematerial mass loading (relative to other materials) associated with thepresently invented cells, reduced proportion of overhead (non-active)components relative to the active material weight/volume, andsurprisingly better utilization of the electrode active material (most,if not all, of the hard carbon particles and Na₃V₂(PO₄)₂F₃ particlescontributing to the sodium ion storage capacity; no dry pockets orineffective spots in the electrode, particularly under highcharge/discharge rate conditions).

The presently invented sodium-ion cells also deliver significantlyhigher power densities than those of conventional cells. This is alsounexpected.

FIG. 7 shows the Ragone plots (both gravimetric and volumetric powerdensity vs. gravimetric and volumetric energy density) of two cells,both containing graphene-embraced Sn nanoparticles as the anode activematerial and NaFePO₄ nanoparticles as the cathode active material. Theexperimental data were obtained from the Na-ion battery cells that wereprepared by the presently invented method (i.e. using anode particulatesand cathode particulates) and those by the conventional slurry coatingof electrodes.

These data indicate that both the gravimetric and volumetric energydensities and power densities of the sodium battery cells prepared bythe presently invented method are significantly higher than those oftheir counterparts prepared via the conventional method. Again, thedifferences are huge. The conventionally made cells exhibit agravimetric energy density of 185 Wh/kg and volumetric energy density of407 Wh/L, but the presently invented cells deliver 289 Wh/kg and 638Wh/L, respectively. The cell-level volumetric energy density of 638 Wh/Lhas never been previously achieved with any conventional rechargeablesodium batteries. The power densities as high as 1444 W/kg and 4,187 W/Lare also unprecedented for typically higher-energy lithium-ionbatteries, let alone for sodium-ion batteries.

These energy density and power density differences are mainly due to thehigh active material mass loading (>25 mg/cm² in the anode and >45mg/cm² in the cathode) associated with the presently invented cells,reduced proportion of overhead (non-active) components relative to theactive material weight/volume, no need to have a binder resin, and theability of the inventive method to better utilize the active materialparticles (all particles being accessible to liquid electrolyte and fastion and electron kinetics).

Shown in FIG. 8 are Ragone plots of sodium metal batteries containing asodium foil as the anode active material, disodium rhodizonate (Na₂C₆O₆)as the cathode active material, and lithium salt (NaPF₆)—PC/DEC asorganic liquid electrolyte. The data are for both sodium metal cellsprepared by the presently invented method and those by the conventionalslurry coating of electrodes. These data indicate that both thegravimetric and volumetric energy densities and power densities of therolled sodium metal cells prepared by the presently invented method aresignificantly higher than those of their counterparts prepared via theconventional method.

Quite noteworthy and unexpected is the observation that the gravimetricenergy density of the presently invented sodium metal-organic cathodecell is as high as 268 Wh/kg, higher than those of all conventionalrechargeable sodium metal or sodium-ion batteries ever reported (recallthat current Na-ion batteries typically store 100-150 Wh/kg based on thetotal cell weight). Furthermore, for organic cathode activematerial-based sodium batteries (even for corresponding lithiumbatteries), a gravimetric power density of 1,200 W/kg and volumetricpower density of 3,465 W/L would have been un-thinkable.

We claim:
 1. A method of producing anode particulates or cathodeparticulates for use in an alkali metal battery, said method comprising:(c) preparing a slurry containing particles of an anode or cathodeactive material capable of reversibly absorbing and desorbing lithiumions or sodium ions, an electron-conducting material, and an electrolytecontaining a lithium salt or sodium salt and an optional polymerdissolved in a liquid solvent; and (d) conducting a particulate-formingmeans to convert said slurry into multiple anode particulates or cathodeparticulates, wherein an anode particulate or a cathode particulate iscomposed of (i) particles of said anode or cathode active material, (ii)said electron-conducting material, and (iii) said electrolyte, whereinsaid electron-conducting material forms a three dimensional network ofelectron-conducting pathways in electronic contact with said anode orcathode active material and said electrolyte forms a three dimensionalnetwork of lithium ion- or sodium ion-conducting channels in ioniccontact with said anode or cathode active material and wherein saidanode particulate or cathode particulate has a dimension from 10 nm to300 μm and an electrical conductivity from about 10⁻⁷ S/cm to about 300S/cm.
 2. The method of claim 1, wherein said particulate-forming meansis selected from pan-coating method, air-suspension coating method,centrifugal extrusion, vibration nozzle method, spray-drying,interfacial polycondensation or interfacial cross-linking, in situpolymerization, matrix polymerization, or a combination thereof.
 3. Themethod of claim 1, wherein said alkali metal battery is a lithium-ionbattery and said anode active material is selected from the groupconsisting of: (a) particles of natural graphite, artificial graphite,mesocarbon microbeads (MCMB), needle coke, carbon particles, carbonfibers, carbon nanotubes, and carbon nanofibers; (b) silicon (Si),germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc(Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium(Ti), iron (Fe), and cadmium (Cd); (c) alloys or intermetallic compoundsof Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, or Cd with other elements, whereinsaid alloys or compounds are stoichiometric or non-stoichiometric; (d)oxides, carbides, nitrides, sulfides, phosphides, selenides, andtellurides of Si, Ge, Sn, Nb, Mo, Pb, Sb, Bi, Zn, Al, Fe, Ni, Co, Ti,Mn, or Cd, and their mixtures or composites; (e) prelithiated versionsthereof; (f) prelithiated graphene sheets; and combinations thereof. 4.The method of claim 1, wherein the alkali metal battery is a sodium-ionbattery and said anode active material contains an alkali intercalationcompound selected from the following groups of materials: (a) sodium- orpotassium-doped silicon (Si), germanium (Ge), tin (Sn), lead (Pb),antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), titanium (Ti),cobalt (Co), nickel (Ni), manganese (Mn), cadmium (Cd), and mixturesthereof; (b) sodium- or potassium-containing alloys or intermetalliccompounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Co, Ni, Mn, Cd, andtheir mixtures; (c) sodium- or potassium-containing oxides, carbides,nitrides, sulfides, phosphides, selenides, tellurides, or antimonides ofSi, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ti, Co, Ni, Mn, Cd, and mixtures orcomposites thereof; (d) sodium or potassium salts; (e) graphene sheetspre-loaded with sodium or potassium; (f) and combinations thereof. 5.The method of claim 1, wherein said alkali metal battery is a sodium-ionbattery and said anode active material contains an alkali intercalationcompound selected from petroleum coke, carbon black, amorphous carbon,activated carbon, hard carbon, soft carbon, templated carbon, hollowcarbon nanowires, hollow carbon sphere, titanates, NaTi₂(PO₄)₃,Na₂Ti₃O₇, Na₂C₈H₄O₄, Na₂TP, Na_(x)TiO₂ (0.2≤x≤1.0), Na₂C₈H₄O₄,carboxylate based materials, C₈H₄Na₂O₄, C₈H₆O₄, C₈H₅NaO₄, C₈Na₂F₄O₄,C₁₀H₂Na₄O₈, C₁₄H₄O₆, C₁₄H₄Na₄O₈, or a combination thereof.
 6. The methodof claim 1, wherein said anode active material contains a prelithiatedSi, prelithiated Ge, prelithiated Sn, prelithiated SnO_(x), prelithiatedSiO_(x), prelithiated iron oxide, prelithiated VO₂, prelithiated Co₃O₄,prelithiated Ni₃O₄, prelithiated Mn₃O₄, or a combination thereof,wherein 1≤x≤2.
 7. The method of claim 1, wherein said anode activematerial is in a form of nanoparticle, nanowire, nanofiber, nanotube,nanosheet, nanobelt, nanoribbon, nanodisc, nanoplatelet, or nanohornhaving a thickness or diameter from 0.5 nm to 100 nm.
 8. The method ofclaim 1, wherein said anode active material is coated with a layer ofcarbon, a conducting polymer, or a graphene sheet.
 9. The method ofclaim 1, wherein said conducting material contains anelectron-conducting polymer selected from polyaniline, polypyrrole,polythiophene, polyfuran, a bi-cyclic polymer, a sulfonated derivativethereof, or a combination thereof.
 10. The method of claim 1, whereinsaid electrolyte has a lithium ion conductivity or sodium ionconductivity from 10⁻⁷ S/cm to 0.05 S/cm at room temperature.
 11. Themethod of claim 1, wherein said electrolyte is selected from an aqueouselectrolyte, an organic liquid electrolyte, an ionic liquid electrolyte,a polymer gel electrolyte, a polymer electrolyte, an inorganic solidstate electrolyte, a quasi-solid electrolyte, or a combination thereof.12. The method of claim 1, wherein said electron-conducting material isselected from a conducting polymer, a carbon fiber or graphite fiber, acarbon nanotube, a carbon nanofiber, a graphitic nanofiber, a conductivepolymer fiber, a metal nanowire, a metal-coated fiber, a graphene sheet,an expanded graphite platelet, carbon black, acetylene black, needlecoke, or a combination thereof.
 13. The method of claim 3, wherein saidprelithiated graphene sheets are selected from prelithiated versions ofpristine graphene, graphene oxide, reduced graphene oxide, graphenefluoride, graphene chloride, graphene bromide, graphene iodide,hydrogenated graphene, nitrogenated graphene, boron-doped graphene,nitrogen-doped graphene, chemically functionalized graphene, aphysically or chemically activated or etched version thereof, or acombination thereof.
 14. The method of claim 1, wherein said cathodeactive material contains a sodium intercalation compound or a potassiumintercalation compound selected from NaFePO₄, Na_((1-x))K_(x)PO₄,KFePO₄, Na_(0.7)FePO₄, Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃, Na₃V₂(PO₄)₂F₃,Na₂FePO₄F, NaFeF₃, NaVPO₄F, KVPO₄F, Na₃V₂(PO₄)₂F₃, Na_(1.5)VOPO₄F_(0.5),Na₃V₂(PO₄)₃, NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅, Na_(x)CoO₂,Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂, Na_(x)(Fe_(1/2)Mn_(1/2))O₂, Na_(x)MnO₂,λ-MnO₂, Na_(x)K_((1-x))MnO₂, Na_(0.44)MnO₂, Na_(0.44)MnO₂/C, Na₄Mn₉O₁₈,NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇, Ni_(1/3)Mn_(1/3)Co_(1/3)O₂,Cu_(0.56)Ni_(0.44)HCF, NiHCF, Na_(x)MnO₂, NaCrO₂, KCrO₂, Na₃Ti₂(PO₄)₃,NiCo₂O₄, Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C, NaV_(1-x)Cr_(x)PO₄F,Se_(z)S_(y), y/z=0.01 to 100, Se, sodium polysulfide, sulfur,Alluaudites, or a combination thereof, wherein 0.1≤x≤1.0.
 15. The methodof claim 1, wherein said cathode active material comprises an alkalimetal intercalation compound or alkali metal-absorbing compound selectedfrom an inorganic material, an organic or polymeric material, a metaloxide/phosphate/sulfide, or a combination thereof.
 16. The method ofclaim 15, wherein said metal oxide/phosphate/sulfide is selected from alithium cobalt oxide, lithium nickel oxide, lithium manganese oxide,lithium vanadium oxide, lithium-mixed metal oxide, lithium ironphosphate, lithium manganese phosphate, lithium vanadium phosphate,lithium mixed metal phosphate, transition metal sulfide, transitionmetal fluoride, transition metal chloride, or a combination thereof. 17.The method of claim 15, wherein said inorganic material is selected fromsulfur, sulfur compound, lithium polysulfide, transition metaldichalcogenide, a transition metal trichalcogenide, or a combinationthereof.
 18. The method of claim 15, wherein said inorganic material isselected from TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, CoO₂, an iron oxide, avanadium oxide, or a combination thereof.
 19. The method of claim 15,wherein said metal oxide/phosphate/sulfide contains a vanadium oxideselected from the group consisting of VO₂, Li_(x)VO₂, V₂O₅, Li_(x)V₂O₅,V₃O₈, Li_(x)V₃O₈, Li_(x)V₃O₇, V₄O₉, Li_(x)V₄O₉, V₆O₁₃, Li_(x)V₆O₁₃,their doped versions, their derivatives, and combinations thereof,wherein 0.1<x<5.
 20. The method of claim 15, wherein said metaloxide/phosphate/sulfide is selected from a layered compound LiMO₂,spinel compound LiM₂O₄, olivine compound LiMPO₄, silicate compoundLi₂MSiO₄, Tavorite compound LiMPO₄F, borate compound LiMBO₃, or acombination thereof, wherein M is a transition metal or a mixture ofmultiple transition metals.
 21. The method of claim 15, wherein saidinorganic material is selected from: (a) bismuth selenide or bismuthtelluride, (b) transition metal dichalcogenide or trichalcogenide, (c)sulfide, selenide, or telluride of niobium, zirconium, molybdenum,hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel,or a transition metal; (d) boron nitride, or (e) a combination thereof.22. The method of claim 15, wherein said organic material or polymericmaterial is selected from poly(anthraquinonyl sulfide) (PAQS), a lithiumoxocarbon, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, quino(triazene), redox-active organic material,tetracyanoquino-dimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxyanthraquinone) (PADAQ), phosphazene disulfide polymer ([(NPS₂)₃]n),lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer,hexaazatrinaphtylene (HATN), hexaazatriphenylene hexacarbonitrile(HAT(CN)₆), 5-benzylidene hydantoin, isatine lithium salt, pyromelliticdiimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi₄),N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAM), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.
 23. The method of claim 22,wherein said thioether polymer is selected frompoly[methanetetryl-tetra(thiomethylene)] (PMTTM),poly(2,4-dithiopentanylene) (PDTP), a polymer containingpoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, poly(2-phenyl-1,3-dithiolane) (PPDT),poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT),poly[1,2,4,5-tetrakis(propylthio)benzene] (PDDTB), orpoly[3,4(ethylenedithio)thiophene] (PEDTT).
 24. The method of claim 15,wherein said organic material contains a phthalocyanine compoundselected from copper phthalocyanine, zinc phthalocyanine, tinphthalocyanine, iron phthalocyanine, lead phthalocyanine, nickelphthalocyanine, vanadyl phthalocyanine, fluorochromium phthalocyanine,magnesium phthalocyanine, manganous phthalocyanine, dilithiumphthalocyanine, aluminum phthalocyanine chloride, cadmiumphthalocyanine, chlorogallium phthalocyanine, cobalt phthalocyanine,silver phthalocyanine, a metal-free phthalocyanine, a chemicalderivative thereof, or a combination thereof.
 25. The method of claim15, wherein said cathode active material contains an alkali metalintercalation compound or alkali metal-absorbing compound selected froman oxide, dichalcogenide, trichalcogenide, sulfide, selenide, ortelluride of niobium, zirconium, molybdenum, hafnium, tantalum,tungsten, titanium, vanadium, chromium, cobalt, manganese, iron, ornickel in a nanowire, nanodisc, nanoribbon, or nanoplatelet form havinga thickness or diameter less than 100 nm.
 26. The method of claim 1,further comprising a step of compacting, merging or bonding a pluralityof said anode particulates to form an anode electrode wherein, prior tosaid anode electrode formation, each particulate has anelectron-conducting material forming a three dimensional network ofelectron-conducting pathways in electronic contact with the anode activematerial and the electrolyte in each particulate forms a threedimensional network of lithium ion- or sodium ion-conducting channels inionic contact with the anode active material and wherein, after saidanode electrode formation, a plurality of three dimensional networks ofelectron-conducting pathways in the plurality of anode particulates aremerged into one large three dimensional network of electron-conductingpathways substantially extended throughout the entire anode electrodeand wherein a plurality of three dimensional networks of lithium ion- orsodium ion-conducting channels in the plurality of anode particulatesare merged into one giant three dimensional network of lithium ion- orsodium ion-conducting channels substantially extended throughout theentire anode electrode.
 27. The method of claim 1, comprising a furtherstep of compacting, merging or bonding a plurality of said cathodeparticulates to form a cathode electrode wherein, prior to said cathodeelectrode formation, each particulate has an electron-conductingmaterial forming a three dimensional network of electron-conductingpathways in electronic contact with the cathode active material and theelectrolyte in each particulate forms a three dimensional network oflithium ion- or sodium ion-conducting channels in ionic contact with thecathode active material and wherein, after said cathode electrodeformation, a plurality of three dimensional networks ofelectron-conducting pathways in the plurality of cathode particulatesare merged into one giant three dimensional network ofelectron-conducting pathways substantially extended throughout theentire cathode electrode and wherein a plurality of three dimensionalnetworks of lithium ion- or sodium ion-conducting channels in theplurality of cathode particulates are merged into one giant threedimensional network of lithium ion- or sodium ion-conducting channelssubstantially extended throughout the entire cathode electrode.
 28. Themethod of claim 26, further comprising combining an optional anodecurrent collector, said anode electrode, a porous separator orsolid-state electrolyte, a cathode electrode, and an optional cathodecurrent collector to form an alkali metal battery.
 29. The method ofclaim 27, further comprising combining an optional anode currentcollector, an anode electrode, a porous separator or solid-stateelectrolyte, said cathode electrode, and an optional cathode currentcollector to form an alkali metal battery.